CVE-2026-100348: kin-openapi spec loader panics on a self-referential additionalProperties $ref (nil-pointer DoS)
kin-openapi is a Go project for handling OpenAPI files. Prior to 0.145.0, openapi3.Loader can dereference a nil SchemaRef.Value while resolving a self-referential additionalProperties JSON Reference such as a schema that points to its own additionalProperties member. Loading an attacker-controlled OpenAPI document through LoadFromData, LoadFromFile, or LoadFromURI reaches resolveComponent before document validation and can panic the loading process. Resolved additionalProperties schemas and ordinary recursive schemas do not take the vulnerable nil-value path. This issue is fixed in version 0.145.0.
Other sources
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 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.
Suggested fix ------------- Add if c.Value == nil { break } (fall through to the nil-safe drillIntoField) before touching c.Value.AdditionalProperties. One line.
Also cleared (stated, not claimed) ---------------------------------- The 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.
Advisory-source note -------------------- Five-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).
Dedup ----- Dedup 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).
Tooling ------- AI 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.
— GitHub
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
go/github.com/getkin/kin-openapito a version that resolves this vulnerability.Fixed in 0.145.0 - Upgrade
Upgrade
kin-openapito a version that resolves this vulnerability.Fixed in 0.145.0
Event History
Frequently Asked Questions
Which applications are exposed to this denial-of-service condition?
Applications using kin-openapi before 0.145.0 are exposed if they load attacker-controlled OpenAPI documents through openapi3.Loader.LoadFromData, LoadFromFile, or LoadFromURI. The malformed reference is processed before document validation, so validation does not prevent the panic.
What input is required to trigger the panic?
An attacker needs to supply an OpenAPI document containing a self-referential additionalProperties JSON Reference, such as a schema referring to its own additionalProperties member. Exploitation does not require privileges or user interaction according to the supplied vector.
Are all recursive OpenAPI schemas affected?
No. Ordinary recursive schemas and resolved additionalProperties schemas do not follow the vulnerable nil-value path. The affected case is an unresolved self-referential additionalProperties $ref.
What remediation is available?
Upgrade kin-openapi to version 0.145.0, which fixes the issue. If upgrading is not immediately possible, avoid loading untrusted OpenAPI documents through the affected loader methods.