RustCrypto: Signatures has timing side-channel in ML-DSA decomposition

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.4 · CVSS:3.1/AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-22705: 0.16% estimated exploitation activity in the next 30 days; percentile 5.51 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A timing side-channel was discovered in the Decompose algorithm which is used during ML-DSA signing to generate hints for the signature. Details The analysis was performed using a constant-time analyzer that examines compiled assembly code for instructions with data-dependent timing behavior. The analyzer flags: - UDIV/SDIV instructions: Hardware division instructions have early termination optimizations where execution time depends on operand values. The decompose function used a hardware division instruction to compute r1.0 / TwoGamma2::U32. This function is called during signing through highbits() and lowbits(), which process values derived from secret key components: - (&w - &cs2).lowbits() where cs2 is derived from secret key component s2 - Hint::new() calls highbits() on values derived from secret key component t0 Original Code: PoC I do not have an exploit written for this, currently. Impact The dividend (r1.0) is derived from secret key material. An attacker with…

Published by the source

13 Jan 2026, 15:10 UTC

Last modified by the source

24 Apr 2026, 19:58 UTC

Source last checked

26 Oct 2026, 15:42 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-hcp2-x6j4-29j7

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# Patch Next advisory brief: CVE-2026-22705

Advisory: RustCrypto: Signatures has timing side-channel in ML-DSA decomposition
IDs: CVE-2026-22705, GHSA-hcp2-x6j4-29j7
Record: https://patchnext.com/advisories/cve-2026-22705 (revision 1, source checked 26 Oct 2026, 15:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ml-dsa 0.1.0-rc.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io ml-dsa: affected <= 0.1.0-rc.2; fixed in 0.1.0-rc.3

## Suggested inspection (read-only)
- crates.io ml-dsa: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on ml-dsa.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-hcp2-x6j4-29j7 (GitHub-reviewed advisory GHSA-hcp2-x6j4-29j7 lists affected ranges: crates.io ml-dsa >=0 <=0.1.0-rc.2)

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