kin-openapi spec loader panics on a self-referential additionalProperties $ref (nil-pointer DoS)

{
  "id": "db7520fdc95f49868d15f9133e52b9b33c0b08a8cf7105fd79f540de64fab670",
  "url": "https://osv.dev/vulnerability/GHSA-mh7x-f8wq-4jhx",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "kin-openapi spec loader panics on a self-referential additionalProperties $ref (nil-pointer DoS)",
    "summary": "The defect ---------- Confirmed at HEAD (f0407d5, v0.144.0). openapi3/loader.go, inside resolveComponent's drill closure (around line 455), the case *SchemaRef branch for pathPart == \"additionalProperties\" dereferences c.Value.AdditionalProperties with no nil-check on c.Value: case *SchemaRef: if pathPart == \"additionalProperties\" { if ap := c.Value.AdditionalProperties.Has; ap != nil { // c.Value can be nil here cursor = *ap } else { cursor = c.Value.AdditionalProperties.Schema } attempted = true } When a $ref fragment drills through .../additionalProperties of a schema whose Value is still nil (a pure, not-yet-resolved $ref, or a self-reference resolved before its own Value is set), c.Value is nil and the .AdditionalProperties access panics. Input and attacker ------------------- A tiny crafted OpenAPI document, one schema, no external refs, no network: openapi: 3.0.3 info: {title: t, version: \"1.0.0\"} paths: {} components: schemas: A: $ref: '#/components/schemas/A/additionalProperties' Attacker model: any service or tool that loads an untrusted spec via the default openapi3.Loader (LoadFromData / LoadFromFile / LoadFromURI), e.g. a spec registry, an API-management platform ingesting user specs, a linter, or a converter. It crashes during LOAD (ResolveRefsIn), before Validate. Verification level ------------------ EXECUTED with negative controls (agent-run go test at HEAD f0407d5, including yesterday's security merge; the bug is still present). The full stack pins LoadFromD",
    "evidence": "osv:GHSA-mh7x-f8wq-4jhx",
    "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-mh7x-f8wq-4jhx",
      "aliases": [
        "CVE-2026-100348",
        "GHSA-mh7x-f8wq-4jhx"
      ],
      "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-mh7x-f8wq-4jhx/GHSA-mh7x-f8wq-4jhx.json",
            "last_known_affected_version_range": "<= 0.144.0"
          }
        }
      ],
      "modified": "2026-10-15T20:30:07.050954802Z",
      "provider": "osv",
      "references": [
        "https://github.com/getkin/kin-openapi/security/advisories/GHSA-mh7x-f8wq-4jhx",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-100348",
        "https://github.com/getkin/kin-openapi/commit/88aa64c7cbd03ecadbb419c473bdcaa8b0124c6b",
        "https://github.com/getkin/kin-openapi",
        "https://github.com/getkin/kin-openapi/releases/tag/v0.145.0"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-476"
        ],
        "severity": "MODERATE",
        "github_reviewed": true,
        "nvd_published_at": "2026-10-15T16:17:30Z",
        "github_reviewed_at": "2026-10-15T20:15:58Z"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-100348",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 336052,
  "published_at": "2026-10-15T20:15:58+00:00"
}