CVE-2021-38195: An issue was discovered in the libsecp256k1 crate before 0.5.0 for Rust

Q: How do I fix CVE-2021-38195?

libsecp256k1: upgrade to 0.5.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-38195 being exploited?

CVE-2021-38195 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-38195 affect?

CVE-2021-38195 affects libsecp256k1. Severity is critical (CVSS 9.8). An issue was discovered in the libsecp256k1 crate before 0.5.0 for Rust. It can verify an invalid signature because it allows the R or S parameter to be larger than the curve order, aka an overflow.

Q: How urgent is CVE-2021-38195?

Priority 59/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-38195 is a critical-severity flaw (CVSS 9.8) affecting libsecp256k1. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in the libsecp256k1 crate before 0.5.0 for Rust. It can verify an invalid signature because it allows the R or S parameter to be larger than the curve order, aka an overflow.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-347
Published	2021-08-08
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: parity

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-08-08 06:15 UTCPublished CVE record published
2026-06-17 04:01 UTCUpdated Record last modified

parity libsecp256k1 UPGRADE

Affected: < 0.5.0

Fixed in: 0.5.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy libsecp256k1 || rpm -q libsecp256k1 || libsecp256k1 --version

2. UPGRADE to 0.5.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade libsecp256k1

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libsecp256k1

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-38195?

libsecp256k1: upgrade to 0.5.0. Exact commands for each OS are on this page.

Is CVE-2021-38195 being exploited?

CVE-2021-38195 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-38195 affect?

CVE-2021-38195 affects libsecp256k1. Severity is critical (CVSS 9.8). An issue was discovered in the libsecp256k1 crate before 0.5.0 for Rust. It can verify an invalid signature because it allows the R or S parameter to be larger than the curve order, aka an overflow.

How urgent is CVE-2021-38195?

Priority 59/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2019-25003 HIGH 7.5 UPGRADE An issue was discovered in the libsecp256k1 crate before 0.3.1 for Rust
CVE-2019-20399 MEDIUM 5.9 UPGRADE A timing vulnerability in the Scalar::check_overflow function in Parity libsecp256k1-rs before 0.3.1 potential

References

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