Vulnerability Description
Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.7.0-beta.9, the `v4_is_invalid()` function in `activitypub-federation-rust` (`src/utils.rs`) does not check for `Ipv4Addr::UNSPECIFIED` (0.0.0.0). An unauthenticated attacker controlling a remote domain can point it to 0.0.0.0, bypass the SSRF protection introduced by the fix for CVE-2025-25194 (GHSA-7723-35v7-qcxw), and reach localhost services on the target server. Version 0.7.0-beta.9 patches the issue.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755
- https://github.com/LemmyNet/lemmy/security/advisories/GHSA-q537-8fr5-cw35
- https://github.com/advisories/GHSA-7723-35v7-qcxw
FAQ
What is CVE-2026-33693?
CVE-2026-33693 is a vulnerability with a CVSS score of 6.5 (MEDIUM). Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.7.0-beta.9, the `v4_is_invalid()` function in `activitypub-federation-rust` (`src/utils.rs`) does not check for `Ipv4Addr::UN...
How severe is CVE-2026-33693?
CVE-2026-33693 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-33693?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.