CVE-2026-100348: Github.com/getkin/kin openapi Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mh7x-f8wq-4jhx",
  "modified" : "2026-10-15T20:15:58Z",
  "published" : "2026-10-15T20:15:58Z",
  "aliases" : [ "CVE-2026-100348" ],
  "summary" : "kin-openapi spec loader panics on a self-referential additionalProperties $ref (nil-pointer DoS)",
  "details" : "The defect\n----------\nConfirmed 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:\n\n    case *SchemaRef:\n        if pathPart == \"additionalProperties\" {\n            if ap := c.Value.AdditionalProperties.Has; ap != nil {   // c.Value can be nil here\n                cursor = *ap\n            } else {\n                cursor = c.Value.AdditionalProperties.Schema\n            }\n            attempted = true\n        }\n\nWhen 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.\n\nInput and attacker\n-------------------\nA tiny crafted OpenAPI document, one schema, no external refs, no network:\n\n    openapi: 3.0.3\n    info: {title: t, version: \"1.0.0\"}\n    paths: {}\n    components:\n      schemas:\n        A:\n          $ref: '#/components/schemas/A/additionalProperties'\n\nAttacker 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.\n\nVerification level\n------------------\nEXECUTED with negative controls (agent-run go test at HEAD f0407d5, including yesterday's security merge; the bug is still present). The full stack pins LoadFromData:196 -> ResolveRefsIn:274 -> resolveSchemaRef:1048 -> resolveComponent:485 -> drill:439 -> :455, propagating to main(); no recover() in loader.go/schema.go (grep + trace). Two negative controls stay clean: drilling additionalProperties of a resolved schema loads fine (the existing TestIssue376 happy path), and a normal recursive schema loads fine, so the nil Value is specifically the cause. I independently re-confirmed at HEAD that loader.go:455 dereferences c.Value.AdditionalProperties with no nil-check on c.Value. NOT verified: I did not enumerate every consumer's recover posture.\n\nSuggested fix\n-------------\nAdd if c.Value == nil { break } (fall through to the nil-safe drillIntoField) before touching c.Value.AdditionalProperties. One line.\n\nAlso cleared (stated, not claimed)\n----------------------------------\nThe allOf/anyOf $ref diamond does not blow up: Schema.validate threads its stack through the return and never pops it, acting as a global pointer-keyed visited-set (executed N=10..30, microseconds). External-ref SSRF/path-traversal is blocked by default (IsExternalRefsAllowed=false); the known custom-ReadFromURIFunc bypass is the already-banked downstream oasdiff item.\n\nAdvisory-source note\n--------------------\nFive-source enumeration: every kin-openapi advisory (CVE-2025-30153 plus the five fresh July-2026 GHSAs) is in openapi3filter (request validation); this finding is in the openapi3 loader, untouched by that systematic reporter and flagged un-analyzed by the prior oasdiff scout. Not contested on the loader surface as of today (a systematic hunter could pivot, so it decays; submit reasonably promptly).\n\nDedup\n-----\nDedup gate clean: no kin-openapi loader verdict in COVERED-INDEX, DISCLOSURE-INDEX or SCOUT-EXCLUDE (the one DISCLOSURE-INDEX hit is report #313, the downstream oasdiff, a different repo/lane).\n\nTooling\n-------\nAI assistance was used while investigating. The panic is executed-verified with negative controls (a one-schema self-referential additionalProperties $ref crashes LoadFromData while a resolved additionalProperties and a normal recursive schema load fine), and I confirmed at HEAD that loader.go:455 dereferences c.Value.AdditionalProperties with no nil-check on c.Value, on a load path with no recover.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/getkin/kin-openapi"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.145.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.144.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/getkin/kin-openapi/security/advisories/GHSA-mh7x-f8wq-4jhx"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-100348"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/getkin/kin-openapi/commit/88aa64c7cbd03ecadbb419c473bdcaa8b0124c6b"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/getkin/kin-openapi"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/getkin/kin-openapi/releases/tag/v0.145.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-476" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-15T20:15:58Z",
    "nvd_published_at" : "2026-10-15T16:17:30Z"
  }
}