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HIGH severity

nistec has Incorrect Calculation in Multiplication of unreduced P-256 scalarsGHSA-f6hc-9g49-xmx7

HIGHFix: FiloSottile/nistec@c58aa12

GHSA-f6hc-9g49-xmx7 is a high-severity (CVSS 7.5) CWE-682 vulnerability in filippo.io/nistec. A fix is available for filippo.io/nistec — see the affected versions and patch details below.

Also known asCVE-2023-24533GO-2023-1595
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-f6hc-9g49-xmx7.

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs52th percentile — riskier than 52% of all scored CVEsHighest risk
0.00%0.39%0.78%1.17%0.2%0.7%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐹filippo.io/nistec

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐹Gofilippo.io/nistecall versions0.0.2go get filippo.io/nistec@v0.0.2

Affected Products

1 product · 1 configurations
Application
nistecnistec_project
< 0.0.2
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for filippo.io/nistec, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update filippo.io/nistec to 0.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f6hc-9g49-xmx7 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

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
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