CVE-2025-8556: Github.com/cloudflare/circl: 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.
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.
Other sources
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.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
github.com/cloudflare/circlto a version that resolves this vulnerability.Fixed in 1.6.1Patch circl-fourq: missing and wrong validation can lead to incorrect results
Event History
Frequently Asked Questions
What is the severity of CVE-2025-8556?
CVE-2025-8556 is a high severity vulnerability due to its potential to compromise session security during key exchange.
How do I fix CVE-2025-8556?
To fix CVE-2025-8556, upgrade Cloudflare CIRCL to version 1.6.1 or later.
What is the impact of CVE-2025-8556?
The impact of CVE-2025-8556 includes the potential for attackers to force the identity point and compromise Diffie-Hellman key exchange security.
Which software is affected by CVE-2025-8556?
CVE-2025-8556 affects Cloudflare CIRCL versions up to 1.6.1.
Does CVE-2025-8556 allow remote exploitation?
Yes, CVE-2025-8556 can be exploited remotely due to the nature of the key exchange vulnerability.