CVE-2026-33693 json
Lemmy's Activitypub-Federation has SSRF via 0.0.0.0 bypass in activitypub-federation-rust v4_is_invalid()
published 7mo ago modified 4mo ago also EUVD-2026-16494 , GHSA-q537-8fr5-cw35
- cvss
- 6.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.4%
- EPSS 0.4% chance of exploitation in 30 days, percentile 31%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- crates.io activitypub_federation 0.7.0-beta.9
- join-lemmy lemmy 0.7.0-beta.9
Is CVE-2026-33693 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 7mo ago
Exploit prediction
0.37% chance of exploitation in the next 30 days, higher than 31% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N |
| GitHub | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| crates.io | activitypub_federation | <0.7.0-beta.9 |
0.7.0-beta.9 |
Affected products
- LemmyNet lemmy
Classification
- Weakness
-
- CWE-918 Server-Side Request Forgery
References
-
github.com
/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755240b7f55d4a5b7665351599
web
-
github.com
/LemmyNet/lemmy/security/advisories/GHSA-q537-8fr5-cw35
web
-
github.com
/advisories/GHSA-7723-35v7-qcxw
advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-33693
advisory
-
github.com
/LemmyNet/activitypub-federation-rust
package
Sources
- CVE List CVE-2026-33693
- GitHub Advisory GHSA-q537-8fr5-cw35
- NVD CVE-2026-33693
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.