kin-openapi is a Go project for handling OpenAPI files. From 0.136.0 until 0.143.0, openapi3filter accepts OpenAPI 3.1 array schemas without an items keyword and then dereferences the nil Schema.Items value while decoding application/x-www-form-urlencoded or multipart/form-data request bodies, response headers, and other array parameter surfaces. A remote unauthenticated client can reach an affected operation with a nonempty request or matching response and deterministically trigger a nil-pointer panic during ValidateRequest or ValidateResponse. OpenAPI 3.0 documents are not affected because document validation rejects arrays without items, and JSON request bodies use a different decoder path. This issue is fixed in version 0.143.0.
https://github.com/getkin/kin-openapi/security/advisories/GHSA-p6wj-qrr4-pgh5
https://github.com/getkin/kin-openapi/releases/tag/v0.143.0
https://github.com/getkin/kin-openapi/commit/30e292371a89ca6d1f91a9553e0aa518b49f838d