Vulnerability RUSTSEC-2026-0426
Summary
LLVM introduces timing-vulnerable optimizations into ML-KEM and ML-DSA operations intended to be constant-time
Details
Summary
On targets that do not have a conditional move/select operations, LLVM compiles the internal conditional_sub_u32() function, into one that will contain a conditional jump on secret-dependent data, which could leak information about encapsulation and signing keys.
conditional_sub_u32() is used throughout the field arithmetic of both ML-KEM and ML-DSA.
Impact
The variable-time jumps have been observed for ML-KEM and ML-DSA on:
i586-unknown-linux-gnus390x-unknown-linux-gnu
Additionally, ML-DSA sees the vulnerable LLVM optimization on x86_64-unknown-linux-gnu, for hazardous::dsa::mldsa44 and hazardous::dsa::mldsa87.
The leakage this LLVM optimization introduces could enable recovery of cryptographic secrets. The practicality of exploiting the leakage depends on the compiler, target CPU used and how "close" to the process using the vulnerable functions the attacker is.
Resolution
Upgrade to v0.17.16 or v0.18.1. conditional_sub_u32() has been re-written to take conditional-move/jump ops availability into account.
Related Vulnerabilities
Other vulnerabilities affecting the same packages
