Summary
CIRCL-Fourq: Missing and wrong validation can lead to incorrect results
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.
The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.
CVE-2025-8556 has a CVSS score of 3.7 (Low). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.6.1); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
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.
Frequently Asked Questions
- What is CVE-2025-8556? CVE-2025-8556 is a low-severity improper input validation vulnerability in github.com/cloudflare/circl (go), affecting versions < 1.6.1. It is fixed in 1.6.1. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
- How severe is CVE-2025-8556? CVE-2025-8556 has a CVSS score of 3.7 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/cloudflare/circl are affected by CVE-2025-8556? github.com/cloudflare/circl (go) versions < 1.6.1 is affected.
- Is there a fix for CVE-2025-8556? Yes. CVE-2025-8556 is fixed in 1.6.1. Upgrade to this version or later.
- Is CVE-2025-8556 exploitable, and should I be worried? Whether CVE-2025-8556 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2025-8556 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2025-8556? Upgrade
github.com/cloudflare/circlto 1.6.1 or later.