CVE-2026-33693 | THREATINT

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.

PUBLISHED Reserved 2026-03-23 | Published 2026-03-27 | Updated 2026-03-30 | Assigner GitHub_M

MEDIUM: 6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Problem types

CWE-918: Server-Side Request Forgery (SSRF)

Product status

< 0.7.0-beta.9

affected

References

github.com/.../lemmy/security/advisories/GHSA-q537-8fr5-cw35

github.com/...ommit/4ae8532b17bc35755240b7f55d4a5b7665351599

github.com/advisories/GHSA-7723-35v7-qcxw

cve.org (CVE-2026-33693)

nvd.nist.gov (CVE-2026-33693)

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