CVE-2026-33693

6.5 mediumEPSS 0.4%

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.

Severity

CVSS 3.1

6.5 medium

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

EPSS: 0.4% chance of exploitation in the next 30 days; higher than 31% of CVEs (scores of 2026-10-31)
CWE: CWE-918
Published: 2026-03-27
Modified: 2026-06-17
Record from: the NVD, synced 2026-10-19

Packages (OSV)

Advisory	Ecosystem	Package	Affected	Fixed in
GHSA-q537-8fr5-cw35	crates.io	activitypub_federation	<0.7.0-beta.9	0.7.0-beta.9

References

https://github.com/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755240b7f55d4a5b7665351599
https://github.com/LemmyNet/lemmy/security/advisories/GHSA-q537-8fr5-cw35
https://github.com/advisories/GHSA-7723-35v7-qcxw

Check your stack JSON