RUSTSEC-2026-0385

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Source

https://rustsec.org/advisories/RUSTSEC-2026-0385

Import Source

https://github.com/rustsec/advisory-db/blob/osv/crates/RUSTSEC-2026-0385.json

JSON Data

https://api.osv.dev/v1/vulns/RUSTSEC-2026-0385

Related

RUSTSEC-2026-0003

Published

2026-10-23T12:00:00Z

Modified

2026-10-23T08:30:02Z

Summary

Non-constant-time mask generation and `u128` comparisons

Details

Summary

The ctutils::Choice type has mask generation functions for each unsigned integer size (u8, u16, u32, u64, u128). These are const fn and therefore can't reuse the asm!-backed mask generation in the cmov crate that's otherwise used to ensure constant-time.

In releases prior to v0.4.4, the generated code from these functions could include a branch on commonly used platforms. This has been corrected in this release and now verified on several platforms using BINSEC.

Additionally, u128 comparison operations provided via ctutils::Choice and intended to work in constant-time were generating branches on 32-bit targets. This has been resolved via a special case implementation of these functions for such targets.

Impact

Branch instructions on secret values can potentially leak such values via covert channels. This can enable attackers to potentially recover such secrets.

Resolution

This has been resolved by calling Choice::to_u8() when generating the mask, which in turn uses black_box as an optimization barrier. Verification that this resulted in the desired change in the generated assembly across a variety of target CPU architectures was performed by BINSEC, which now runs automatically in CI using cargo checkct.

Database specific

{
    "license":  "CC-BY-4.0"
}

References

Affected packages

crates.io / ctutils

Package

Name: ctutils; View open source insights on deps.dev
Purl: pkg:cargo/ctutils

Affected ranges

Type: SEMVER
Events: Introduced

0.0.0-0

Fixed

0.4.4

Ecosystem specific

{
    "affected_functions":  null,
    "affects":  {
        "arch":  [],
        "functions":  [],
        "os":  []
    }
}