{"id":"RUSTSEC-2026-0385","revision":"bd8330234ad541fdb1f62d17a7aafec0","records":[{"revision":"bd8330234ad541fdb1f62d17a7aafec0","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"RUSTSEC-2026-0385","aliases":[],"title":"Non-constant-time mask generation and `u128` comparisons","description":"## Summary\n\nThe `ctutils::Choice` type has mask generation functions for each unsigned\ninteger size (`u8`, `u16`, `u32`, `u64`, `u128`). These are `const fn` and\ntherefore can't reuse the `asm!`-backed mask generation in the `cmov` crate\nthat's otherwise used to ensure constant-time.\n\nIn releases prior to v0.4.4, the generated code from these functions could\ninclude a branch on commonly used platforms. This has been corrected in this\nrelease and now verified on several platforms using BINSEC.\n\nAdditionally, `u128` comparison operations provided via `ctutils::Choice` and\nintended to work in constant-time were generating branches on 32-bit targets.\nThis has been resolved via a special case implementation of these functions\nfor such targets.\n\n## Impact\n\nBranch instructions on secret values can potentially leak such values via\ncovert channels. This can enable attackers to potentially recover such secrets.\n\n## Resolution\n\nThis has been resolved by calling `Choice::to_u8()` when generating the mask,\nwhich in turn uses `black_box` as an optimization barrier. Verification that\nthis resulted in the desired change in the generated assembly across a variety\nof target CPU architectures was performed by BINSEC, which now runs\nautomatically in CI using `cargo checkct`.","state":0,"publishedAt":"2026-10-23T12:00:00+00:00","modifiedAt":"2026-10-23T08:30:02.3895751+00:00","affected":[{"ecosystem":"crates.io","name":"ctutils","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0.0.0-0"},{"kind":"fixed","version":"0.4.4"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[],"references":["https://crates.io/crates/ctutils","https://rustsec.org/advisories/RUSTSEC-2026-0385.html","https://github.com/RustCrypto/utils/pull/1569"],"sourceUrl":"https://osv.dev/vulnerability/RUSTSEC-2026-0385","license":"OSV · upstream source license applies","key":"osv:RUSTSEC-2026-0385","identifiers":["RUSTSEC-2026-0385"]},"retained":false,"historicalAffected":[]}],"coverage":[]}