Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The Go module github.com/cloudflare/circl, versions before 1.6.1, has flawed FourQ point validation: it fails to reject user-supplied low-order points during Diffie-Hellman key exchange, and ScalarMult has incorrect point validation that can produce wrong results in isEqual. The source gives few details on exactly what an attacker must do, but the advisory says it could force the identity point and compromise session security. Upgrade to version 1.6.1, which mitigates these issues.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 3.7 | Low | 3.1 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N | CNA (redhat) |
- CISA KEV Not listed.
- EPSS 0.0053, the 45th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:14 UTC First seen by agentprime
- 31 Oct 2026, 14:14 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-2x5j-vhc8-9cwm
- OSV: GHSA-2x5j-vhc8-9cwm
- github.com/cloudflare/circl/security/advisories/GHSA-2x5j-vhc8-9cwm
- nvd.nist.gov/vuln/detail/CVE-2025-8556
- access.redhat.com/security/cve/CVE-2025-8556
- bugzilla.redhat.com/show_bug.cgi?id=2371624
- github.com/cloudflare/circl
- github.com/cloudflare/circl/tree/v1.6.1
- news.ycombinator.com/item?id=45669593
- www.botanica.software/blog/cryptographic-issues-in-cloudflares-circl-fourq-implementation