CVE-2026-33693
MEDIUMLemmy's Activitypub-Federation has SSRF via 0.0.0.0 bypass in activitypub-federation-rust v4_is_invalid()
Title source: cnaDescription
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.
Exploits (1)
References (3)
Core 3
Core References
X_Refsource_Confirm x_refsource_confirm
https://github.com/LemmyNet/lemmy/security/advisories/GHSA-q537-8fr5-cw35
X_Refsource_Misc x_refsource_misc
https://github.com/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755240b7f55d4a5b7665351599
X_Refsource_Misc x_refsource_misc
https://github.com/advisories/GHSA-7723-35v7-qcxw
Scores
CVSS v3
6.5
EPSS
0.0002
EPSS Percentile
6.2%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
CISA SSVC
Vulnrichment
Exploitation
poc
Automatable
yes
Technical Impact
partial
Details
CWE
CWE-918
Status
published
Products (2)
crates.io/activitypub_federation
0 - 0.7.0-beta.9crates.io
LemmyNet/lemmy
< 0.7.0-beta.9
Published
Mar 27, 2026
Tracked Since
Mar 27, 2026