kin-openapi: Unauthenticated panic (DoS) in openapi3filter legacy router via non-canonical/unsupported HTTP method on a static path

{
  "id": "bb4d0c2fe42a24d8a92ab5e6eea8f593806e0020120379a9ef116068b3ec151a",
  "url": "https://osv.dev/vulnerability/GHSA-fh4f-47mf-f2gj",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "kin-openapi: Unauthenticated panic (DoS) in openapi3filter legacy router via non-canonical/unsupported HTTP method on a static path",
    "summary": "## Summary The `openapi3filter.ValidationHandler` (the exported, documented request-validation middleware) hard-wires the legacy router (`routers/legacy`). That router matches the incoming request method verbatim against a trie built exclusively from upper-cased canonical HTTP methods. A request carrying a method token that is not one of the 9 standard methods — a legitimate-but-unsupported token such as `PROPFIND`, or a non-canonical case variant such as lowercase `get` — misses the trie, leaves `route == nil`, and for an existing **static** path falls through to `PathItem.GetOperation(method)`, whose `default:` case calls `panic(...)`. The panic fires inside route resolution, **before any authentication** runs. This is an unauthenticated, remotely triggerable denial of service (recovered per-connection panic + unbounded error-log growth). ## Root Cause - `openapi3filter/validation_handler.go:39` — `ValidationHandler.Load()` always constructs `legacyrouter.NewRouter(doc)`; there is no alternative router option on this path. - `routers/legacy/router.go:109` — the request method is used verbatim (`method, url := req.Method, ...`); there is no canonicalization or rejection of unknown method tokens. - `routers/legacy/router.go:69-70` — the trie is populated with `strings.ToUpper(method)` keys taken from `pathItem.Operations()` (canonical `http.Method*` constants only). - `routers/legacy/router.go:141` — `root.Match(method + \" \" + remainingPath)` misses for a non-canonical/unsupp",
    "evidence": "osv:GHSA-fh4f-47mf-f2gj",
    "products": [
      {
        "name": {
          "value": "github.com/getkin/kin-openapi",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "0.145.0",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "GHSA-fh4f-47mf-f2gj",
      "aliases": [
        "CVE-2026-100347",
        "GHSA-fh4f-47mf-f2gj"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "0.145.0"
                }
              ]
            }
          ],
          "package": {
            "name": "github.com/getkin/kin-openapi",
            "purl": "pkg:golang/github.com/getkin/kin-openapi",
            "ecosystem": "Go"
          },
          "database_specific": {
            "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-fh4f-47mf-f2gj/GHSA-fh4f-47mf-f2gj.json",
            "last_known_affected_version_range": "<= 0.144.0"
          }
        }
      ],
      "modified": "2026-10-15T20:30:11.858476899Z",
      "provider": "osv",
      "references": [
        "https://github.com/getkin/kin-openapi/security/advisories/GHSA-fh4f-47mf-f2gj",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-100347",
        "https://github.com/getkin/kin-openapi/commit/f1a5b523b82868d2d9be2e116b4e942892be72c3",
        "https://github.com/getkin/kin-openapi",
        "https://github.com/getkin/kin-openapi/releases/tag/v0.145.0"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-20",
          "CWE-248"
        ],
        "severity": "MODERATE",
        "github_reviewed": true,
        "nvd_published_at": "2026-10-15T16:17:30Z",
        "github_reviewed_at": "2026-10-15T20:15:48Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-100347",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 336060,
  "published_at": "2026-10-15T20:15:48+00:00"
}