---
cve: "CVE-2026-33693"
severity: "MEDIUM"
cvss: 6.5
epss: "36%"
vendor: "LemmyNet"
kev: false
exploited: false
published: "2026-03-27 01:16:18"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-09-07T05:48:20+02:00"
---

# CVE-2026-33693

> 6.5 MEDIUM · 🧪 PoC

## Beschreibung

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.

## CVSS-Vektor

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

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Gering | warn |
| I Integrität | Gering | warn |
| A Verfügbarkeit | Keine | good |

## Patch verfügbar (OSV)

- 4ae8532b17bc35755240b7f55d4a5b7665351599 (Commit)

## Referenzen

- <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>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-33693) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_