Caddy forward_auth copy_headers Does Not Strip Client-Supplied Headers, Allowing Identity Injection and Privilege Escalation

{
  "id": "72b32cc570f89877e1831fb3e0bfeba1460fc17b072f3e076e80b20c358b1043",
  "url": "https://osv.dev/vulnerability/CVE-2026-30851",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Caddy forward_auth copy_headers Does Not Strip Client-Supplied Headers, Allowing Identity Injection and Privilege Escalation",
    "summary": "Caddy is an extensible server platform that uses TLS by default. From version 2.10.0 to before version 2.11.2, forward_auth copy_headers does not strip client-supplied headers, allowing identity injection and privilege escalation. This issue has been patched in version 2.11.2.",
    "evidence": "osv:CVE-2026-30851",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-30851",
      "aliases": [
        "CVE-2026-30851",
        "GHSA-7r4p-vjf4-gxv4",
        "GO-2026-4639"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/caddyserver/caddy",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fb22a26b1a08a2fa3b2526d1852467904ee140f6"
                },
                {
                  "fixed": "ffb6ab0644f24c5ee6542aca6bd59b7a1b0a8f91"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "2.10.0"
                      },
                      {
                        "fixed": "2.11.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "cpe": "cpe:2.3:a:caddyserver:caddy:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "2.10.0"
                      },
                      {
                        "fixed": "2.11.2"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "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"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-30851.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:33.259011558Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/30xxx/CVE-2026-30851.json",
        "https://github.com/caddyserver/caddy/security/advisories/GHSA-7r4p-vjf4-gxv4",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-30851",
        "https://github.com/caddyserver/caddy/issues/6610",
        "https://github.com/caddyserver/caddy/pull/6608",
        "https://github.com/caddyserver/caddy/pull/7545"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-287",
          "CWE-345"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/30xxx/CVE-2026-30851.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-30851",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 500455,
  "published_at": "2026-03-07T16:28:37.097+00:00"
}