CVE-2026-42180

The record

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.

Affected packages

Related vulnerabilities

• GHSA-3jvj-v6w2-h948 Lemmy has SSRF in /api/v3/post via Webmention dispatch Same vulnerability
• CVE-2026-42181 Lemmy is a link aggregator and forum for the fediverse. Also affects lemmy_api_common
• GHSA-h6hf-9846-xwrq Lemmy has SSRF and internal image disclosure in post link metadata via unvalidated… Also affects lemmy_api_common
• CVE-2026-114730 Roundcube Webmail 1.6.14 before 1.6.20 and 1.7.0 before 1.7.5 is affected by a… CWE-918
• CVE-2026-87953 Server-Side Request Forgery (SSRF) vulnerability in Drupal SAML SSO - Service Provider… CWE-918
• CVE-2026-114634 WWBN AVideo before 29.4.0 contains a blind server-side request forgery vulnerability in… CWE-918
• CVE-2026-112288 Krayin CRM 2.2.5 before 2.2.7 contains a server-side request forgery filter bypass that… CWE-918
• CVE-2026-111936 Sigma File Manager through 2.2.0 contains a server-side request forgery vulnerability… CWE-918