CIRCL-Fourq: Missing and wrong validation can lead to incorrect results

LOW 3.7CVE-2025-8556 · GHSA-2x5j-vhc8-9cwm · GO-2025-3754 · Published 06/08/2025 · updated 27/10/2026

Package	Affected versions	Patched versions
github.com/cloudflare/circl Go	`< 1.6.1`	`1.6.1`

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.

NVD description

A flaw was found in CIRCL's implementation of the FourQ elliptic curve. This vulnerability allows an attacker to compromise session security via low-order point injection and incorrect point validation during Diffie-Hellman key exchange.

References

cloudflare/circl security advisory · WEB
nvd.nist.gov/vuln/detail/CVE-2025-8556 · ADVISORY
access.redhat.com/security/cve/CVE-2025-8556 · WEB
bugzilla.redhat.com/show_bug.cgi · WEB
cloudflare/circl · PACKAGE
cloudflare/circl · WEB
news.ycombinator.com/item · WEB
botanica.software/blog/cryptographic-issues-in-cloudflares-circl-fourq-implementation · WEB

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Package

Affected versions

Patched versions

github.com/cloudflare/circl

< 1.6.1

1.6.1

Description

Impact

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.

NVD description