CVE-2026-42180

MEDIUM EPSS 8.1%
Published May 8, 20261mo ago · Modified Jun 17, 20261w ago
6.3 CVSS 3.1
Medium
Find Similar
Published May 8, 2026 1mo ago
Last Modified Jun 17, 2026 1w ago

Description

Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.19.18, Lemmy allows an authenticated low-privileged user to create a link post through POST /api/v3/post. When a post is created in a public community, the backend asynchronously sends a Webmention to the attacker-controlled link target. The submitted URL is checked for syntax and scheme, but the audited code path does not reject loopback, private, or link-local destinations before the Webmention request is issued. This lets a normal user trigger server-side HTTP requests toward internal services. This issue has been patched in version 0.19.18.

CVSS Details

Base Score
6.3
Exploitability
2.8
Impact
3.4
Vector string
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
Attack Vector Network
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality Low
Integrity Low
Availability Low

Threat Intelligence

EPSS Exploit Probability
8.1% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-918 Server-Side Request Forgery (SSRF) Validation

References 2

  • github.com https://github.com/LemmyNet/lemmy/releases/tag/0.19.18
  • github.com https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.