Vulnerability-Lookup

GHSA-239G-2685-54X3

Vulnerability from github – Published: 2026-07-06 19:54 – Updated: 2026-07-06 19:54

Summary

install: TOCTOU symlink race (unlink-then-create without O_EXCL) allows arbitrary file overwrite

Details

copy_file in install/src/install.rs removes the destination then recreates it by pathname via File::create / fs::copy without O_EXCL/create_new. Between the unlink and the recreate, a local attacker with write access to the destination directory can drop in a symlink and redirect the write.

Impact: when install runs privileged into an attacker-writable directory (staging/build paths), the race allows redirecting writes to arbitrary files and overwriting sensitive system files (/etc/passwd, /etc/shadow). Recommendation: create atomically with create_new/O_EXCL and copy via the opened fd rather than reopening by path.

Remediation: Acknowledged by Canonical; fixed in commit b5bbabc1.

Reported by Zellic in the uutils coreutils Program Security Assessment (prepared for Canonical, Jan 20 2026), audited commit 3a07ffc5a9bd4c283e75afa548ba1f1957bad242. Finding 3.50. Credit: Zellic.

Severity

6.3 (Medium)


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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "crates.io",
        "name": "uu_install"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.6.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-35355"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-367",
      "CWE-59"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-06T19:54:08Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "`copy_file` in `install/src/install.rs` removes the destination then recreates it by pathname via `File::create` / `fs::copy` without `O_EXCL`/`create_new`. Between the unlink and the recreate, a local attacker with write access to the destination directory can drop in a symlink and redirect the write.\n\n**Impact:** when `install` runs privileged into an attacker-writable directory (staging/build paths), the race allows redirecting writes to arbitrary files and overwriting sensitive system files (`/etc/passwd`, `/etc/shadow`). Recommendation: create atomically with `create_new`/`O_EXCL` and copy via the opened fd rather than reopening by path.\n\n**Remediation:** Acknowledged by Canonical; fixed in commit b5bbabc1.\n\n---\n_Reported by Zellic in the *uutils coreutils Program Security Assessment* (prepared for Canonical, Jan 20 2026), audited commit `3a07ffc5a9bd4c283e75afa548ba1f1957bad242`. Finding 3.50. Credit: Zellic._",
  "id": "GHSA-239g-2685-54x3",
  "modified": "2026-07-06T19:54:08Z",
  "published": "2026-07-06T19:54:08Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/uutils/coreutils/security/advisories/GHSA-239g-2685-54x3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-35355"
    },
    {
      "type": "WEB",
      "url": "https://github.com/uutils/coreutils/pull/10067"
    },
    {
      "type": "WEB",
      "url": "https://github.com/uutils/coreutils/commit/b5bbabc18a1121908848d836f869a4e98eb63886"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/uutils/coreutils"
    },
    {
      "type": "WEB",
      "url": "https://github.com/uutils/coreutils/releases/tag/0.6.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "install: TOCTOU symlink race (unlink-then-create without O_EXCL) allows arbitrary file overwrite"
}

CVE-2026-35355 (GCVE-0-2026-35355)

Vulnerability from cvelistv5 – Published: 2026-04-22 16:08 – Updated: 2026-04-22 18:01

Title

uutils coreutils install Arbitrary File Overwrite via Symlink TOCTOU Race

Summary

The install utility in uutils coreutils is vulnerable to a Time-of-Check to Time-of-Use (TOCTOU) race condition during file installation. The implementation unlinks an existing destination file and then recreates it using a path-based operation without the O_EXCL flag. A local attacker can exploit the window between the unlink and the subsequent creation to swap the path with a symbolic link, allowing them to redirect privileged writes to overwrite arbitrary system files.

Severity

6.3 (Medium)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-04-22 18:01 UTC

CWE

CWE-367 - Time-of-Check Time-of-Use (TOCTOU) Race Condition

Assigner

canonical mitre root

References

2 references

URL	Tags
https://github.com/uutils/coreutils/pull/10067	issue-trackingpatch
https://github.com/uutils/coreutils/releases/tag/0.6.0	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
Uutils	coreutils	Affected: 0 , < 0.6.0 (semver)

Credits

Zellic

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-35355",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-22T18:01:44.426332Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-04-22T18:01:47.122Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/uutils/coreutils/pull/10067"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://github.com/uutils",
          "defaultStatus": "unaffected",
          "packageName": "coreutils",
          "platforms": [
            "Linux",
            "Unix",
            "macOS"
          ],
          "product": "coreutils",
          "repo": "https://github.com/uutils/coreutils",
          "vendor": "Uutils",
          "versions": [
            {
              "lessThan": "0.6.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Zellic"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "The install utility in uutils coreutils is vulnerable to a Time-of-Check to Time-of-Use (TOCTOU) race condition during file installation. The implementation unlinks an existing destination file and then recreates it using a path-based operation without the O_EXCL flag. A local attacker can exploit the window between the unlink and the subsequent creation to swap the path with a symbolic link, allowing them to redirect privileged writes to overwrite arbitrary system files."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-29",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-29: Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions"
            }
          ]
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      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "LOCAL",
            "availabilityImpact": "HIGH",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "HIGH",
            "privilegesRequired": "LOW",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H",
            "version": "3.1"
          },
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          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
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      ],
      "problemTypes": [
        {
          "descriptions": [
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              "cweId": "CWE-367",
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      "providerMetadata": {
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          "tags": [
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            "patch"
          ],
          "url": "https://github.com/uutils/coreutils/pull/10067"
        },
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://github.com/uutils/coreutils/releases/tag/0.6.0"
        }
      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "title": "uutils coreutils install Arbitrary File Overwrite via Symlink TOCTOU Race"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "cc1ad9ee-3454-478d-9317-d3e869d708bc",
    "assignerShortName": "canonical",
    "cveId": "CVE-2026-35355",
    "datePublished": "2026-04-22T16:08:14.960Z",
    "dateReserved": "2026-04-02T12:58:56.087Z",
    "dateUpdated": "2026-04-22T18:01:47.122Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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GHSA-239G-2685-54X3

CVE-2026-35355 (GCVE-0-2026-35355)

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