CVE-2026-33693 Details
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.
A server-side request forgery (SSRF) vulnerability has been identified in the Lemmy ActivityPub federation library, specifically in versions prior to 0.7.0-beta.9. The issue arises in the 'v4_is_invalid()' function within 'src/utils.rs', which fails to validate 'Ipv4Addr::UNSPECIFIED' (0.0.0.0). This oversight allows an unauthenticated attacker controlling a remote domain to bypass the SSRF protections implemented in response to CVE-2025-25194. Exploitation of this vulnerability enables access to localhost services on the target server.
Users should update to Lemmy version 0.7.0-beta.9 or later, where this vulnerability has been patched.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Mar 27, 2026CISA-ADP
Assessed Mar 30, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/advisories/GHSA-7723-35v7-qcxw | [email protected] | AdvisoryBundleVendor |
| https://github.com/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755240b7f55d4a5b7665351599 | [email protected] | Source CodeVendor |
| https://github.com/LemmyNet/lemmy/security/advisories/GHSA-q537-8fr5-cw35 | [email protected] | AdvisoryExploitRemedyVendor |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-918 | Server-Side Request Forgery (SSRF) | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Lemmy | All versions |
CPE
Remediation
| |
| LemmyNet activitypub-federation-rust | All versions |
CPE
Remediation
| |
Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Mar 27, 2026 | New CVE Received | [email protected] |