Medium severity6.5NVD Advisory· Published Mar 27, 2026· Updated Apr 28, 2026
CVE-2026-33693
CVE-2026-33693
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.
Affected packages
Versions sourced from the GitHub Security Advisory.
| Package | Affected versions | Patched versions |
|---|---|---|
activitypub_federationcrates.io | < 0.7.0-beta.9 | 0.7.0-beta.9 |
Affected products
1Patches
14ae8532b17bcAdd some more IP checks (#162)
1 file changed · +2 −0
src/utils.rs+2 −0 modified@@ -20,6 +20,8 @@ fn v4_is_invalid(v4: Ipv4Addr) -> bool { || v4.is_link_local() || v4.is_multicast() || v4.is_documentation() + || v4.is_unspecified() + || v4.is_broadcast() } fn v6_is_invalid(v6: Ipv6Addr) -> bool {
Vulnerability mechanics
Generated by null/stub on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
5- github.com/advisories/GHSA-7723-35v7-qcxwnvdADVISORY
- github.com/advisories/GHSA-q537-8fr5-cw35ghsaADVISORY
- nvd.nist.gov/vuln/detail/CVE-2026-33693ghsaADVISORY
- github.com/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755240b7f55d4a5b7665351599nvdWEB
- github.com/LemmyNet/lemmy/security/advisories/GHSA-q537-8fr5-cw35nvdWEB
News mentions
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