kin-openapi: Uncontrolled Recursion on Circular allOf/anyOf/oneOf Schemas Causes Fatal Process Crash

{
  "id": "3147ae515a8284b0d56ee9219118eb39b3d008df27db5fe74a3f0976ca57f11a",
  "url": "https://osv.dev/vulnerability/GHSA-g8cf-rcjf-c8cf",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "kin-openapi: Uncontrolled Recursion on Circular allOf/anyOf/oneOf Schemas Causes Fatal Process Crash",
    "summary": "## Summary kin-openapi's spec loader and spec-time validator both handle circular schema references safely: the loader resolves circular `$ref`s on purpose (to support recursive data structures), and `Schema.validate()` uses stack-based cycle detection. `Validate()` therefore accepts a schema whose `allOf` / `anyOf` / `oneOf` chain refers back to itself, returning no error. The runtime validators do not have that protection. When such a schema is used for request or response validation, the recursion through the combinator chain is unbounded. In Go this produces a **fatal stack overflow** (`runtime: goroutine stack exceeds ... limit` / `fatal error: stack overflow`), which is **not** a recoverable panic. `recover()` cannot catch it, so `net/http`'s per-connection recovery does not help. The entire process is terminated, including all goroutines serving unrelated clients. Two independent unguarded recursion sites were confirmed: 1. `openapi3/schema.go` — `visitJSON` / `visitXOFOperations` (reached by `VisitJSON`, i.e. response validation and direct schema validation). 2. `openapi3filter/req_resp_decoder.go` — `decodeValue` (reached first during request parameter decoding). The report also identifies the same gap in `urlValuesDecoder.parseValue` and `buildResObj`/`buildFromSchemas`. ## Details ### Root Cause `Schema.validate()` has cycle detection (`openapi3/schema.go:1396`): ```go func (schema *Schema) validate(ctx context.Context, stack []*Schema) ([]*Schema, error) { if slic",
    "evidence": "osv:GHSA-g8cf-rcjf-c8cf",
    "products": [
      {
        "name": {
          "value": "github.com/getkin/kin-openapi",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "0.149.0",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "GHSA-g8cf-rcjf-c8cf",
      "aliases": [
        "CVE-2026-100354",
        "GHSA-g8cf-rcjf-c8cf"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "0.149.0"
                }
              ]
            }
          ],
          "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-g8cf-rcjf-c8cf/GHSA-g8cf-rcjf-c8cf.json"
          }
        }
      ],
      "modified": "2026-10-15T20:30:04.351750747Z",
      "provider": "osv",
      "references": [
        "https://github.com/getkin/kin-openapi/security/advisories/GHSA-g8cf-rcjf-c8cf",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-100354",
        "https://github.com/getkin/kin-openapi/commit/9245cef66c840e27a08409a8a5cd0ee930c5bcff",
        "https://github.com/getkin/kin-openapi",
        "https://github.com/getkin/kin-openapi/releases/tag/v0.149.0"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-674"
        ],
        "severity": "HIGH",
        "github_reviewed": true,
        "nvd_published_at": "2026-10-15T17:17:07Z",
        "github_reviewed_at": "2026-10-15T20:20:37Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-100354",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 336040,
  "published_at": "2026-10-15T20:20:37+00:00"
}