http4k disabled replay protection in Digest authentication default configuration

Severity: medium · CVSS 5.3 · Published 2026-06-19

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.

Technologies: Http4k-Security-Digest. Vendors: Http4k.

Quick answers

Is This vulnerability exploited in the wild?
No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
How severe is This vulnerability?
Medium severity, with a CVSS score of 5.3, published 19 June 2026.
Which products and versions are affected?
Http4k-Security-Digest < 4.51.0.0, >= 5.0.0.0 < 5.42.0.0, >= 6.0.0.0 < 6.48.0.0.
Is there a fix for This vulnerability?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is This vulnerability attacked?
It is attacked over the network, in a software library.
Am I affected?
Check whether you run Http4k-Security-Digest at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

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

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