CVE-2026-42180

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 v3 6.3 MEDIUM

6.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 3.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact LOW

Integrity Impact LOW

Availability Impact LOW

Scope UNCHANGED

References

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

Configurations

No configuration.

History

13 May 2026, 18:16

Type	Values Removed	Values Added
References	~~() https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948 -~~	() https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948 -

08 May 2026, 20:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-05-08 20:16

Updated : 2026-06-17 10:47

NVD link : CVE-2026-42180

Mitre link : CVE-2026-42180

CVE.ORG link : CVE-2026-42180

JSON object : View

Products Affected

No product.

CWE

CWE-918

Server-Side Request Forgery (SSRF)

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