CVE-2026-33693

MEDIUM SEVERITY

CVSS Score & Metrics

Base Score

6.5 / 10

Vector String

                                        CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N                                    

Vulnerability 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.

Vulnerability Details

Published Date

March 25, 2026

Last Modified

March 30, 2026

CWE ID

CWE-918

Source

GitHub

Vendor

rust

Product

activitypub_federation

External References

https://github.com/LemmyNet/lemmy/security/advisories/GHSA-q537-8fr5-cw35
https://github.com/LemmyNet/activitypub-federation-rust/commit/4ae8532b17bc35755240b7f55d4a5b7665351599
https://github.com/advisories/GHSA-7723-35v7-qcxw
https://github.com/advisories/GHSA-q537-8fr5-cw35

CVE-2026-33693

CVSS Score & Metrics

Vulnerability Description

Vulnerability Details

External References

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