Vulnerability-Lookup

UBUNTU-CVE-2026-27590 (CVE-2026-27590)

Vulnerability from osv_ubuntu – Published: 2026-02-24 17:29 – Updated: 2026-07-02 16:11 – Source website

Details

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode because strings.ToLower() can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect SCRIPT_NAME/SCRIPT_FILENAME and PATH_INFO, potentially causing a request that contains .php to execute a different on-disk file than intended (path confusion). In setups where an attacker can control file contents (e.g., upload features), this can lead to unintended PHP execution of non-.php files (potential RCE depending on deployment). Version 2.11.1 fixes the issue.

Severity

8.9 (High)


                    
                      CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P

9.8 (Critical)


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

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-27590	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-27590	REPORT
	https://github.com/caddyserver/caddy/security/adv…	REPORT
	https://github.com/caddyserver/caddy/releases/tag…	REPORT
	https://github.com/php/frankenphp/security/adviso…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "caddy",
            "binary_version": "2.6.2-6ubuntu0.24.04.3+esm2"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:24.04:LTS",
        "name": "caddy",
        "purl": "pkg:deb/ubuntu/caddy@2.6.2-6ubuntu0.24.04.3+esm2?arch=source\u0026distro=esm-apps/noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.6.2-6",
        "2.6.2-6ubuntu0.24.04.1",
        "2.6.2-6ubuntu0.24.04.2",
        "2.6.2-6ubuntu0.24.04.2+esm1",
        "2.6.2-6ubuntu0.24.04.3",
        "2.6.2-6ubuntu0.24.04.3+esm1",
        "2.6.2-6ubuntu0.24.04.3+esm2"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "caddy",
            "binary_version": "2.6.2-12"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:25.10",
        "name": "caddy",
        "purl": "pkg:deb/ubuntu/caddy@2.6.2-12?arch=source\u0026distro=questing"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.6.2-9",
        "2.6.2-11",
        "2.6.2-12"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "caddy",
            "binary_version": "2.6.2-14ubuntu0.26.04.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:26.04:LTS",
        "name": "caddy",
        "purl": "pkg:deb/ubuntu/caddy@2.6.2-14ubuntu0.26.04.1~esm1?arch=source\u0026distro=esm-apps/resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.6.2-12",
        "2.6.2-14",
        "2.6.2-14ubuntu0.26.04.1~esm1"
      ]
    }
  ],
  "aliases": [],
  "details": "Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy\u0027s FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode because `strings.ToLower()` can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect `SCRIPT_NAME`/`SCRIPT_FILENAME` and `PATH_INFO`, potentially causing a request that contains `.php` to execute a different on-disk file than intended (path confusion). In setups where an attacker can control file contents (e.g., upload features), this can lead to unintended PHP execution of non-.php files (potential RCE depending on deployment). Version 2.11.1 fixes the issue.",
  "id": "UBUNTU-CVE-2026-27590",
  "modified": "2026-07-02T16:11:59Z",
  "published": "2026-02-24T17:29:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-27590"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-27590"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/caddyserver/caddy/security/advisories/GHSA-5r3v-vc8m-m96g"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/caddyserver/caddy/releases/tag/v2.11.1"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/php/frankenphp/security/advisories/GHSA-g966-83w7-6w38"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P",
      "type": "CVSS_V4"
    },
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-27590"
  ]
}

CVE-2026-27590 (GCVE-0-2026-27590)

Vulnerability from cvelistv5 – Published: 2026-02-24 16:33 – Updated: 2026-02-27 20:52

Title

Caddy: Unicode case-folding length expansion causes incorrect split_path index (SCRIPT_NAME/PATH_INFO confusion) in FastCGI transport

Summary

Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy's FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode because `strings.ToLower()` can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect `SCRIPT_NAME`/`SCRIPT_FILENAME` and `PATH_INFO`, potentially causing a request that contains `.php` to execute a different on-disk file than intended (path confusion). In setups where an attacker can control file contents (e.g., upload features), this can lead to unintended PHP execution of non-.php files (potential RCE depending on deployment). Version 2.11.1 fixes the issue.

Severity

8.9 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P

SSVC

Exploitation: poc Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-02-27 20:51 UTC

CWE

CWE-20 - Improper Input Validation
CWE-180 - Incorrect Behavior Order: Validate Before Canonicalize

Assigner

GitHub_M mitre root Scorecard

References

3 references

URL	Tags
https://github.com/caddyserver/caddy/security/adv…	x_refsource_CONFIRM
https://github.com/php/frankenphp/security/adviso…	x_refsource_MISC
https://github.com/caddyserver/caddy/releases/tag…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
caddyserver	caddy	Affected: < 2.11.1

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-27590",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-02-27T20:51:50.628047Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-02-27T20:52:00.327Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "caddy",
          "vendor": "caddyserver",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.11.1"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Caddy is an extensible server platform that uses TLS by default. Prior to version 2.11.1, Caddy\u0027s FastCGI path splitting logic computes the split index on a lowercased copy of the request path and then uses that byte index to slice the original path. This is unsafe for Unicode because `strings.ToLower()` can change UTF-8 byte length for some characters. As a result, Caddy can derive an incorrect `SCRIPT_NAME`/`SCRIPT_FILENAME` and `PATH_INFO`, potentially causing a request that contains `.php` to execute a different on-disk file than intended (path confusion). In setups where an attacker can control file contents (e.g., upload features), this can lead to unintended PHP execution of non-.php files (potential RCE depending on deployment). Version 2.11.1 fixes the issue."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.9,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-20",
              "description": "CWE-20: Improper Input Validation",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-180",
              "description": "CWE-180: Incorrect Behavior Order: Validate Before Canonicalize",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-02-24T16:33:41.353Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/caddyserver/caddy/security/advisories/GHSA-5r3v-vc8m-m96g",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/caddyserver/caddy/security/advisories/GHSA-5r3v-vc8m-m96g"
        },
        {
          "name": "https://github.com/php/frankenphp/security/advisories/GHSA-g966-83w7-6w38",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/php/frankenphp/security/advisories/GHSA-g966-83w7-6w38"
        },
        {
          "name": "https://github.com/caddyserver/caddy/releases/tag/v2.11.1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/caddyserver/caddy/releases/tag/v2.11.1"
        }
      ],
      "source": {
        "advisory": "GHSA-5r3v-vc8m-m96g",
        "discovery": "UNKNOWN"
      },
      "title": "Caddy: Unicode case-folding length expansion causes incorrect split_path index (SCRIPT_NAME/PATH_INFO confusion) in FastCGI transport"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-27590",
    "datePublished": "2026-02-24T16:33:41.353Z",
    "dateReserved": "2026-02-20T17:40:28.450Z",
    "dateUpdated": "2026-02-27T20:52:00.327Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

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.

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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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UBUNTU-CVE-2026-27590 (CVE-2026-27590)

CVE-2026-27590 (GCVE-0-2026-27590)

Tags

Sightings

Nomenclature

Related by attack behaviour