{"id":"CVE-2026-33693","aliases":["GHSA-q537-8fr5-cw35"],"url":"https://o3.security/vulnerability/CVE-2026-33693","summary":"Lemmy's Activitypub-Federation has SSRF via 0.0.0.0 bypass in activitypub-federation-rust v4_is_invalid()","details":"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":"2026-03-27T00:03:35.946Z","modified":"2026-08-12T03:51:30.078239059Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"crates.io","name":"activitypub_federation","fixedVersion":"0.7.0-beta.9"}],"fix":{"url":"https://github.com/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755240b7f55d4a5b7665351599","label":"LemmyNet/activitypub-federation-rust@4ae8532"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33693.json"},{"type":"ADVISORY","url":"https://github.com/LemmyNet/lemmy/security/advisories/GHSA-q537-8fr5-cw35"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-7723-35v7-qcxw"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33693"},{"type":"FIX","url":"https://github.com/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755240b7f55d4a5b7665351599"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:30.078239059Z"}}