What’s Vulnerable › Vulnerabilities

CVE-2026-73501: kin-openapi: ValidationHandler.Load() Fail-Open Authentication Bypass via NoopAuthenticationFunc Default

• Severity: critical (CVSS 9.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-12 · updated 2026-10-24
• Weakness: CWE-287

Description

kin-openapi is a Go project for handling OpenAPI files. Prior to 0.144.0, ValidationHandler.Load() in openapi3filter/validation_handler.go silently replaces a nil AuthenticationFunc with NoopAuthenticationFunc, which returns nil without checking credentials. This substitution causes every OpenAPI security requirement to be satisfied for unauthenticated requests when an application relies on ValidationHandler as its enforcement middleware. The no-op callback prevents the fail-closed ErrAuthenticationServiceMissing path from being reached and forwards the request to protected handlers that may require an API key, OAuth token, or another security scheme. This issue is fixed in version 0.144.0.

Affected products

• getkin kin-openapi: before 0.144.0

References

• https://github.com/getkin/kin-openapi/commit/f0407d53b0730280266f454b755010e7eeb985da
• https://github.com/getkin/kin-openapi/releases/tag/v0.144.0
• https://github.com/getkin/kin-openapi/security/advisories/GHSA-r277-6w6q-xmqw
• https://github.com/getkin/kin-openapi/security/advisories/GHSA-r277-6w6q-xmqw

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