caddy — security advisory

{
  "id": "8f91bee4517a1e5ac45ffa8511eceeef572ab4d9ab44bf2c6938b1d991a81d0e",
  "url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-27590",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "DEBIAN-CVE-2026-27590",
    "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.",
    "evidence": "osv:DEBIAN-CVE-2026-27590",
    "products": [
      {
        "name": {
          "value": "caddy",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.6.2-5+deb12u1",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "2.6.2-5",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "caddy",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.6.2-12+deb13u1",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "2.6.2-12",
            "evidence": "/affected/1/versions"
          }
        ]
      },
      {
        "name": {
          "value": "caddy",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "2.11.2-1",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "2.11.2-1~bpo13+1",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "2.6.2-12",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "2.6.2-13",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "2.6.2-14",
            "evidence": "/affected/2/versions"
          }
        ]
      }
    ],
    "severity": "critical",
    "structured": {
      "id": "DEBIAN-CVE-2026-27590",
      "aliases": [
        "DEBIAN-CVE-2026-27590"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.6.2-5+deb12u1"
                }
              ]
            }
          ],
          "package": {
            "name": "caddy",
            "purl": "pkg:deb/debian/caddy?arch=source&distro=bookworm",
            "ecosystem": "Debian:12"
          },
          "versions": [
            "2.6.2-5"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27590.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.6.2-12+deb13u1"
                }
              ]
            }
          ],
          "package": {
            "name": "caddy",
            "purl": "pkg:deb/debian/caddy?arch=source&distro=trixie",
            "ecosystem": "Debian:13"
          },
          "versions": [
            "2.6.2-12"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27590.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "2.11.2-1"
                }
              ]
            }
          ],
          "package": {
            "name": "caddy",
            "purl": "pkg:deb/debian/caddy?arch=source&distro=forky",
            "ecosystem": "Debian:14"
          },
          "versions": [
            "2.11.2-1~bpo13+1",
            "2.6.2-12",
            "2.6.2-13",
            "2.6.2-14"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27590.json"
          },
          "ecosystem_specific": {
            "urgency": "not yet assigned"
          }
        }
      ],
      "modified": "2026-10-24T18:00:07.180314132Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-27590"
      ],
      "references": [
        "https://security-tracker.debian.org/tracker/CVE-2026-27590"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-27590",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 444075,
  "published_at": "2026-02-24T17:29:04.493+00:00"
}