CVE-2025-8556 — circl
LOWCVE-2025-8556 is a low-severity (CVSS 3.7) CWE-1287 vulnerability in github.com/cloudflare/circl. A fix is available for github.com/cloudflare/circl — see the affected versions and patch details below.
Github.com/cloudflare/circl: circl-fourq: missing and wrong validation can lead to incorrect results
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 CVE-2025-8556.
EPSS Exploitation Probability
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
github.com/cloudflare/circlReal-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
Impact
The CIRCL implementation of FourQ fails to validate user-supplied low-order points during Diffie-Hellman key exchange, potentially allowing attackers to force the identity point and compromise session security.
Moreover, there is an incorrect point validation in ScalarMult can lead to incorrect results in the isEqual function and if a point is on the curve.
Patches
Version 1.6.1 (https://github.com/cloudflare/circl/tree/v1.6.1) mitigates the identified issues.
We acknowledge Alon Livne (Botanica Software Labs) for the reported findings.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/cloudflare/circl | all versions | 1.6.1go get github.com/cloudflare/circl@v1.6.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cloudflare/circl, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/cloudflare/circl to 1.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-8556 is resolved across your whole dependency graph.
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.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.Source: Red Hat security advisory for CVE-2025-8556 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2025-8556 in your dependencies?
Find it across Go, including transitive dependencies.