nistec has Incorrect Calculation in Multiplication of unreduced P-256 scalars

Exploitation

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

CVSS

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

EPSS

• CVE-2023-24533: 0.67% estimated exploitation activity in the next 30 days; percentile 52.20 (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.

Multiplication of certain unreduced P-256 scalars produce incorrect results. There are no protocols known at this time that can be attacked due to this. From the fix commit notes: Unlike the rest of nistec, the P-256 assembly doesn't use complete addition formulas, meaning that p256PointAdd[Affine]Asm won't return the correct value if the two inputs are equal. This was (undocumentedly) ignored in the scalar multiplication loops because as long as the input point is not the identity and the scalar is lower than the order of the group, the addition inputs can't be the same. As part of the math/big rewrite, we went however from always reducing the scalar to only checking its length, under the incorrect assumption that the scalar multiplication loop didn't require reduction.

Published by the source

1 Mar 2023, 22:36 UTC

Last modified by the source

20 May 2024, 21:48 UTC

Source last checked

26 Oct 2026, 15:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-f6hc-9g49-xmx7

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# Patch Next advisory brief: CVE-2023-24533

Advisory: nistec has Incorrect Calculation in Multiplication of unreduced P-256 scalars
IDs: CVE-2023-24533, GHSA-f6hc-9g49-xmx7
Record: https://patchnext.com/advisories/cve-2023-24533 (revision 1, source checked 26 Oct 2026, 15:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: filippo.io/nistec 0.0.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go filippo.io/nistec: affected < 0.0.2; fixed in 0.0.2

## Suggested inspection (read-only)
- Go filippo.io/nistec: 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 filippo.io/nistec.
- 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-f6hc-9g49-xmx7 (GitHub-reviewed advisory GHSA-f6hc-9g49-xmx7 lists affected ranges: Go filippo.io/nistec >=0 <0.0.2)

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