GHSA-FHVH-VW7H-9XF3: Cryptographic Signature Forgery via AVX2 Logic Error in libcrux-ml-dsa

Vulnerability ID: GHSA-FHVH-VW7H-9XF3
CVSS Score: 8.2
Published: 2026-05-19

A critical logic vulnerability in the libcrux-ml-dsa library allows cryptographic signature forgery on x86_64 architectures using the AVX2 backend. The flaw originates from an incorrect SIMD implementation of the ML-DSA use_hint function, violating FIPS 204 specifications and allowing attackers to bypass signature verification.

TL;DR

The libcrux-ml-dsa library mishandles the use_hint function in its AVX2 implementation. Attackers can exploit this logic error to forge ML-DSA signatures that are improperly validated on affected hardware platforms.

⚠️ Exploit Status: POC

Technical Details

CWE ID: CWE-347, CWE-681
Attack Vector: Network
CVSS v4.0: 8.2 (High)
Exploit Status: Proof of Concept (PoC) available via Wycheproof vectors
Impact: Cryptographic Signature Forgery
Affected Architecture: x86_64 (AVX2)

Affected Systems

Systems executing libcrux-ml-dsa versions prior to 0.0.9 on x86_64 architectures with AVX2 instruction sets.
libcrux-ml-dsa: < 0.0.9 (Fixed in: 0.0.9)

Exploit Details

GitHub (C2SP/wycheproof): Wycheproof test vectors designed to exercise the use_hint edge case and validate the vulnerability.

Mitigation Strategies

Upgrade the libcrux-ml-dsa dependency to version 0.0.9 or higher.
Disable the AVX2 backend to force the usage of the portable Rust implementation.

Remediation Steps:

Identify all projects utilizing libcrux-ml-dsa via Software Composition Analysis (SCA).
Update the Cargo.toml file to mandate libcrux-ml-dsa version 0.0.9.
Recompile the application to statically link the updated library.
Execute Wycheproof test vectors to validate the correct handling of the use_hint algorithm.
Deploy the recompiled application to the production environment.