GHSA-xrf2-5r3p-5wgj libcrux: Panic in Signature Hint Decoding During Verification

• crates.io libcrux-ml-dsa: < 0.0.8 → fixed in 0.0.8

During ML-DSA verification the serialized hint values are decoded as specified in algorithm 22 `HintBitUnpack` of FIPS 204, subsection 7.1. The algorithm requires that the cumulative hint counters per row of the hint vector are strictly increasing and below a maximum value which depends on the choice of ML-DSA parameter set (line 4). In libcrux-ml-dsa, hint decoding did not check the boundedness of the cumulative hint counter of the last row of the hint vector. Impact A manipulated invalid hint can cause an out-of-bounds memory access since the hint decoding logic may attempt to read outside the bounds of the serialized signature, causing a runtime panic. Mitigation Starting from version `0.0.8`, hint decoding will check the cumulative hint counter of the last row as well.