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MEDIUM severity

CVE-2019-20399 — libsecp256k1-rs

MEDIUMFix: paritytech/libsecp256k1@11ba23a

CVE-2019-20399 is a medium-severity (CVSS 5.9) CWE-203 vulnerability in libsecp256k1-rs. A fix is available for libsecp256k1-rs — see the affected versions and patch details below.

Observable Discrepancy in libsecp256k1-rs

Also known asGHSA-7cqg-8449-rmfvRUSTSEC-2020-0156
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs58th percentile — riskier than 58% of all scored CVEsHighest risk
0.00%0.46%0.92%1.38%0.4%0.9%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2019-20399 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🦀libsecp256k1-rs

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

Description

A timing vulnerability in the Scalar::check_overflow function in Parity libsecp256k1-rs before 0.3.1 potentially allows an attacker to leak information via a side-channel attack.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🦀crates.iolibsecp256k1-rsall versions0.3.1cargo update -p libsecp256k1-rs --precise 0.3.1

Affected Products

1 product · 1 configurations
Application
libsecp256k1parity
< 0.3.1
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 libsecp256k1-rs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update libsecp256k1-rs to 0.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-20399 is resolved across your whole dependency graph.

  3. Workarounds

    Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Frequently Asked Questions

A timing vulnerability in the Scalar::check_overflow function in Parity libsecp256k1-rs before 0.3.1 potentially allows an attacker to leak information via a side-channel attack.
O3 Security · Impact-Aware SCA

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CVE-2019-20399: libsecp256k1 — Fixed in 0.3.1