Executive brief
A security flaw was identified in the http4k library, which provides tools for building web applications. The library's Digest authentication feature was configured by default to skip critical security checks that prevent attackers from reusing intercepted login credentials. If an attacker captures a user's authentication data, they could potentially reuse it to gain unauthorized access to protected resources without knowing the user's password.
Technical details
A capture-replay vulnerability (CWE-294) exists in http4k's `ServerFilters.DigestAuth` and `DigestAuthProvider` components. By default, the `nonceVerifier` parameter was set to a function that always returned true, meaning the server did not validate the uniqueness, age, or prior use of the nonce provided by the client. An attacker who intercepts a valid `Authorization: Digest` header (e.g., through network sniffing or log access) can replay that header to authenticate as the user indefinitely. The fix removes the insecure default, requiring developers to explicitly provide a secure nonce verification implementation.
Affected products
- http4k http4k-security-digest < 4.51.0.0, >= 5.0.0.0 < 5.42.0.0, >= 6.0.0.0 < 6.48.0.0
Timeline
- 2021-07-11: other: Vulnerable default introduced in version 4.x
- 2026-06-16: disclosed: Advisory published by maintainers
- 2026-06-19: advisory: GitHub Advisory published
References
- https://github.com/http4k/http4k/security/advisories/GHSA-c7jm-38gq-h67h
- https://github.com/http4k/http4k/commit/4f904b4692
- https://github.com/http4k/http4k/commit/8a52b615b1
- https://datatracker.ietf.org/doc/html/rfc7616
- https://github.com/http4k/http4k/releases/tag/6.48.0.0
- https://api.github.com/repos/http4k/http4k/security-advisories/GHSA-c7jm-38gq-h67h