curve25519-dalek has timing variability in curve25519-dalek's Scalar29::sub/Scalar52::sub

Exploitation

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

CVSS

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

EPSS

• CVE-2024-58262: 0.18% estimated exploitation activity in the next 30 days; percentile 7.65 (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.

Timing variability of any kind is problematic when working with potentially secret values such as elliptic curve scalars, and such issues can potentially leak private keys and other secrets. Such a problem was recently discovered in curve25519-dalek. The Scalar29::sub (32-bit) and Scalar52::sub (64-bit) functions contained usage of a mask value inside a loop where LLVM saw an opportunity to insert a branch instruction (jns on x86) to conditionally bypass this code section when the mask value is set to zero as can be seen in godbolt: - 32-bit (see L106): https://godbolt.org/z/zvaWxzvqv - 64-bit (see L48): https://godbolt.org/z/PczYj7Pda A similar problem was recently discovered in the Kyber reference implementation: https://groups.google.com/a/list.nist.gov/g/pqc-forum/c/hqbtIGFKIpU/m/cnE3pbueBgAJ As discussed on that thread, one portable solution, which is also used in this PR, is to introduce a volatile read as an optimization barrier, which prevents the compiler from optimizing it…

Published by the source

18 Jun 2024, 21:56 UTC

Last modified by the source

17 Feb 2026, 19:30 UTC

Source last checked

26 Oct 2026, 15:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-x4gp-pqpj-f43q

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# Patch Next advisory brief: CVE-2024-58262

Advisory: curve25519-dalek has timing variability in `curve25519-dalek`'s `Scalar29::sub`/`Scalar52::sub`
IDs: CVE-2024-58262, GHSA-x4gp-pqpj-f43q
Record: https://patchnext.com/advisories/cve-2024-58262 (revision 1, source checked 26 Oct 2026, 15:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: curve25519-dalek 4.1.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- crates.io curve25519-dalek: affected < 4.1.3; fixed in 4.1.3

## Suggested inspection (read-only)
- crates.io curve25519-dalek: 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 curve25519-dalek.
- 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-x4gp-pqpj-f43q (GitHub-reviewed advisory GHSA-x4gp-pqpj-f43q lists affected ranges: crates.io curve25519-dalek >=0 <4.1.3)

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