Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The activitypub_federation crate before 0.7.0-beta.9 does not reject the unspecified address 0.0.0.0 (or its IPv4-mapped IPv6 form) in its SSRF protection, so requests to it are not blocked. A remote attacker who controls a domain can point that domain at 0.0.0.0 and have the library reach services listening on the target server's localhost, such as internal services. Upgrade to activitypub_federation 0.7.0-beta.9 or later. The source does not describe a workaround.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 6.5 | Medium | 3.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0038, the 32nd percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 15:18 UTC First seen by agentprime
- 31 Oct 2026, 15:18 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-q537-8fr5-cw35
- OSV: GHSA-q537-8fr5-cw35
- github.com/LemmyNet/lemmy/security/advisories/GHSA-q537-8fr5-cw35
- nvd.nist.gov/vuln/detail/CVE-2026-33693
- github.com/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755240b7f55d4a5b7665351599
- github.com/LemmyNet/activitypub-federation-rust
- github.com/advisories/GHSA-7723-35v7-qcxw