kin-openapi openapi3filter: nil-pointer panic in ValidateResponse on a response header declared with content

Why it is Amber

• CVSS 8.2 high
• Remotely exploitable without logging in
• On your watchlist: Go

Affected packages

References

• https://github.com/advisories/GHSA-74vm-87hj-r66f
• https://github.com/getkin/kin-openapi/security/advisories/GHSA-74vm-87hj-r66f
• https://nvd.nist.gov/vuln/detail/CVE-2026-100349
• https://github.com/getkin/kin-openapi/commit/f5441d67f855ed34d975b3b85665764644ab1459
• https://github.com/getkin/kin-openapi/releases/tag/v0.146.0
• https://github.com/advisories/GHSA-74vm-87hj-r66f

Original description

kin-openapi is a Go project for handling OpenAPI files. Prior to 0.146.0, openapi3filter.ValidateResponse passes a nil response header schema to decodeValue when an OpenAPI document declares the header with content instead of schema. The document passes validation, but every response validation for the affected operation dereferences the nil schema and panics even when the response does not contain the declared header. Applications that ingest an untrusted specification can expose this as remote availability impact, while applications using only trusted local specifications still crash when the affected operation is exercised. This issue is fixed in version 0.146.0.