Monitor vulnerabilities like this one.
Sign up free to get alerted when software you use is affected.
6.5
Activitypub-Federation allows attackers to access internal services
GHSA-q537-8fr5-cw35
CVE-2026-33693
Summary
An attacker can control a remote domain and access services on the target server by sending traffic to 0.0.0.0. This is due to a missing check in the Activitypub-Federation code. To mitigate this, update to the latest version of Activitypub-Federation and ensure that your server configuration does not allow unauthenticated access to internal services.
What to do
- Update activitypub_federation to version 0.7.0-beta.9.
Affected software
| Vendor | Product | Affected versions | Fix available |
|---|---|---|---|
| – | activitypub_federation | <= 0.7.0-beta.9 | 0.7.0-beta.9 |
Original title
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:...
Original 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.
ghsa CVSS3.1
6.5
Vulnerability type
CWE-918
Server-Side Request Forgery (SSRF)
Published: 27 Mar 2026 · Updated: 27 Mar 2026 · First seen: 25 Mar 2026