RUSTSEC-2026-0387
Multiple timing variability issues in operations intended to be constant-time
Summary
Several operations intended to be constant-time could execute secret-dependent branches, depending on the compiler and target CPU. These include subtraction, zero counting, division, and Montgomery multiplication.
Additionally, UintRef equality could terminate at the first unequal limb,
and BoxedMontyForm::invert branched on whether an inverse exists.
Impact
Applications using affected operations on secret integers may leak information through timing or microarchitectural side channels. This includes information about intermediate arithmetic values, matching limbs, and invertibility.
Such leakage could potentially enable recovery of cryptographic secrets. Practical exploitability depends on the downstream algorithm, compiler, target CPU, and an attacker's ability to observe the side channel.
Resolution
Upgrade to v0.7.6, which removes the identified branches, updates ctutils to
include its constant-time fixes, and adds BINSEC-based regression checks using
cargo checkct for arithmetic on multiple targets.
What each source reports
OSV No score
Multiple timing variability issues in operations intended to be constant-time
Summary
Several operations intended to be constant-time could execute secret-dependent branches, depending on the compiler and target CPU. These include subtraction, zero counting, division, and Montgomery multiplication.
Additionally, UintRef equality could terminate at the first unequal limb,
and BoxedMontyForm::invert branched on whether an inverse exists.
Impact
Applications using affected operations on secret integers may leak information through timing or microarchitectural side channels. This includes information about intermediate arithmetic values, matching limbs, and invertibility.
Such leakage could potentially enable recovery of cryptographic secrets. Practical exploitability depends on the downstream algorithm, compiler, target CPU, and an attacker's ability to observe the side channel.
Resolution
Upgrade to v0.7.6, which removes the identified branches, updates ctutils to
include its constant-time fixes, and adds BINSEC-based regression checks using
cargo checkct for arithmetic on multiple targets.
- Record
RUSTSEC-2026-0387- Updated
- 2026-11-02
Affected packages
| Package | Affected | Fixed |
|---|---|---|
crypto-bigintcrates.io |
0.0.0-0 up to 0.7.6 | 0.7.6 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
RUSTSEC-2026-0387 is a vulnerability with no CVSS score yet in crypto-bigint, published October 23, 2026. No source lists public exploit code. Fixed in crypto-bigint 0.7.6.