Caddy: Unsafe Unicode Handling in FastCGI splitPos Allows Execution of Non-PHP Files

{
  "id": "f1845665500f50366ce3c7ce9b9ab5f11a1178dd8fed761ad9d7eaffa676bb5e",
  "url": "https://osv.dev/vulnerability/CVE-2026-45135",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Caddy: Unsafe Unicode Handling in FastCGI splitPos Allows Execution of Non-PHP Files",
    "summary": "Caddy is an extensible server platform that uses TLS by default. From 2.7.0 until 2.11.3, the FastCGI transport's splitPos() in modules/caddyhttp/reverseproxy/fastcgi/fastcgi.go misuses golang.org/x/text/search with search.IgnoreCase when the request path contains a non-ASCII byte. Two distinct flaws in that fallback let an attacker mislead Caddy's FastCGI splitting into treating a non-.php (or other configured split_path extension) file as a script. In any deployment where the attacker can place content into a file served via FastCGI (uploads, file storage, etc.), this can be escalated to remote code execution by crafting a URL whose path triggers either flaw. This vulnerability is fixed in 2.11.3.",
    "evidence": "osv:CVE-2026-45135",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-45135",
      "aliases": [
        "CVE-2026-45135",
        "GHSA-m675-2p33-xv9g",
        "GO-2026-5492"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/caddyserver/caddy",
              "type": "GIT",
              "events": [
                {
                  "introduced": "cd486c25d168caf58f4b6fe5d3252df9432901ec"
                },
                {
                  "fixed": "cc58caa1099240ef1a4c280b892260b380a85c86"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "2.7.0"
                      },
                      {
                        "fixed": "2.11.3"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "cpe": "cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.7.0"
                      },
                      {
                        "fixed": "2.11.3"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v2.11.2",
            "v2.11.1",
            "v2.11.0",
            "v2.11.0-beta.2",
            "v2.11.0-beta.1",
            "v2.10.2",
            "v2.10.1",
            "v2.10.0",
            "v2.10.0-beta.4",
            "v2.10.0-beta.3",
            "v2.9.1",
            "v2.10.0-beta.2",
            "v2.10.0-beta.1",
            "v2.9.0",
            "v2.9.0-beta.3",
            "v2.9.0-beta.2",
            "v2.9.0-beta.1",
            "v2.8.4",
            "v2.8.3",
            "v2.8.2",
            "v2.8.1",
            "v2.8.0",
            "v2.8.0-rc.1",
            "v2.8.0-beta.2",
            "v2.8.0-beta.1",
            "v2.7.5",
            "v2.7.4",
            "v2.7.3",
            "v2.7.2",
            "v2.7.1",
            "v2.7.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-45135.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.425023659Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45135.json",
        "https://github.com/caddyserver/caddy/security/advisories/GHSA-m675-2p33-xv9g",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-45135"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-176",
          "CWE-178",
          "CWE-20"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45135.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-45135",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504899,
  "published_at": "2026-06-23T17:56:42.662+00:00"
}