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

Advisory record · `GHSA-2x5j-vhc8-9cwm`

- **Identifiers:** `GHSA-2x5j-vhc8-9cwm` · `CVE-2025-8556` · `GO-2025-3754`
- **State:** Confirmed
- **Severity:** CVSS 3.7 Low
- **Critical:** No
- **Weakness (CWE):** [CWE-20](https://cwe.mitre.org/data/definitions/20.html) · [CWE-347](https://cwe.mitre.org/data/definitions/347.html) · [CWE-1287](https://cwe.mitre.org/data/definitions/1287.html)
- **Tags:** [Weak cryptography or TLS](https://agentprime.io/advisories/tag/weak-crypto.md) · [CWE-20](https://agentprime.io/advisories/tag/cwe-20.md) · [CWE-1287](https://agentprime.io/advisories/tag/cwe-1287.md)
- **Published:** 10 Jun 2025
- **Updated:** 10 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 10 Jun 2025, 21:18 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/cloudflare/circl` (Go): affected `<1.6.1`; fixed in `1.6.1`

## 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.

Written 1 Nov 2026.

## 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

- 3.7 Low, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N`, from 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](https://osv.dev/vulnerability/GHSA-2x5j-vhc8-9cwm)

## Sources

- [GitHub Advisory Database: GHSA-2x5j-vhc8-9cwm](https://github.com/advisories/GHSA-2x5j-vhc8-9cwm)
- [OSV: GHSA-2x5j-vhc8-9cwm](https://osv.dev/vulnerability/GHSA-2x5j-vhc8-9cwm)
- <https://github.com/cloudflare/circl/security/advisories/GHSA-2x5j-vhc8-9cwm>
- <https://nvd.nist.gov/vuln/detail/CVE-2025-8556>
- <https://access.redhat.com/security/cve/CVE-2025-8556>
- <https://bugzilla.redhat.com/show_bug.cgi?id=2371624>
- <https://github.com/cloudflare/circl>
- <https://github.com/cloudflare/circl/tree/v1.6.1>
- <https://news.ycombinator.com/item?id=45669593>
- <https://www.botanica.software/blog/cryptographic-issues-in-cloudflares-circl-fourq-implementation>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-2x5j-vhc8-9cwm>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-2x5j-vhc8-9cwm/>. Everything for agents: <https://agentprime.io/llms.txt>.