CVE-2026-54147 in http4k
Summary
by MITRE • 09/18/2026
http4k is a functional toolkit for Kotlin HTTP applications. Prior to 4.51.0.0, 5.42.0.0, and 6.50.0.0, DigestAuthProvider.verify in http4k-security-digest ignores its configured algorithm parameter and verifies every Digest response with hardcoded MD5. Deployments configured for SHA-256 therefore receive weaker MD5-based verification, exposing Digest authentication to collision-related attack paths that depend on the hash function's collision resistance. This issue is fixed in versions 4.51.0.0, 5.42.0.0, and 6.50.0.0.
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Analysis
by VulDB Data Team • 09/18/2026
The http4k library serves as a functional toolkit for building HTTP applications within the Kotlin ecosystem, providing developers with utilities to handle various aspects of web service communication including authentication mechanisms. Among these is the DigestAuthProvider component, which implements RFC 2617 compliant digest authentication protocols. This mechanism relies on cryptographic hash functions to ensure that credentials are not transmitted in plaintext while verifying the integrity and authenticity of requests between clients and servers. The security model of digest authentication depends heavily on the strength of the underlying hash algorithm chosen by the deployment configuration, typically allowing for either MD5 or SHA-256 depending on server capabilities and client support.
A critical implementation flaw was identified in versions prior to 4.51.0.0, 5.42.0.0, and 6.50.0.0 of the http4k-security-digest module. Specifically, the verify method within DigestAuthProvider failed to respect the algorithm parameter configured by the application developer or system administrator. Instead of dynamically selecting the hash function based on this configuration, the implementation hardcoded MD5 as the sole verification mechanism regardless of whether SHA-256 was explicitly requested for enhanced security. This represents a significant deviation from expected behavior where the cryptographic strength should align with organizational policy and threat models that mandate stronger hashing algorithms to mitigate known weaknesses in older standards.
The operational impact of this vulnerability is substantial, particularly for deployments that have intentionally configured their systems to use SHA-256 for digest authentication. By forcing MD5 verification, these systems are exposed to collision-related attack paths that exploit the mathematical vulnerabilities inherent in the MD5 hash function. Although practical remote attacks against HTTP Digest Authentication using MD5 collisions remain complex and require specific conditions such as control over both client and server or sophisticated man-in-the-middle scenarios, the reduction of cryptographic strength lowers the barrier for potential attackers. This weakness undermines the confidentiality and integrity guarantees that digest authentication is designed to provide, potentially allowing malicious actors to forge valid request signatures if they can generate MD5 collisions efficiently enough within their specific attack context.
From a classification perspective, this issue aligns with CWE-327 which describes the use of a broken or risky cryptographic algorithm. The failure to enforce the configured security policy also touches upon aspects of CWE-693 related to protection mechanism failures where the system does not properly protect against attacks that exploit weaknesses in its own implementation logic. In terms of adversary tactics, this vulnerability could be leveraged within ATT&CK techniques involving credential access or defense evasion if an attacker can manipulate authentication flows by exploiting the predictable and weaker hash output, although it is primarily a configuration enforcement failure rather than a direct exploitation vector for immediate remote code execution.
To mitigate this risk, organizations utilizing http4k must upgrade to version 4.51.0.0, 5.42.0.0, or later versions of the security-digest module where the algorithm parameter is correctly respected during verification processes. It is imperative that development teams audit their dependency trees and ensure that all instances of DigestAuthProvider are instantiated with updated libraries that enforce cryptographic agility as intended by the specification. Additionally, security reviews should verify that configuration files explicitly define SHA-256 for digest authentication to prevent fallback behaviors or misconfigurations in future deployments, ensuring that the system adheres to modern cryptographic standards and maintains robust protection against hash collision attacks.