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.
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2025-8556US | — | — | ||
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 incor… | ||||
references
External citations — patches, advisories, analysis.
- https://access.redhat.com/security/cve/CVE-2025-8556WEB
- https://bugzilla.redhat.com/show_bug.cgi?id=2371624WEB
- https://github.com/cloudflare/circlPACKAGE
- https://github.com/cloudflare/circl/security/advisories/GHSA-2x5j-vhc8-9cwmWEB
- https://github.com/cloudflare/circl/tree/v1.6.1WEB
- https://news.ycombinator.com/item?id=45669593WEB
- https://nvd.nist.gov/vuln/detail/CVE-2025-8556ADVISORY
- https://www.botanica.software/blog/cryptographic-issues-in-cloudflares-circl-fourq-implementationWEB
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