CVE-2026-54742

The record

Lemmy is a link aggregator and forum for the fediverse. From 0.19.18 until 0.19.19 and 1.0.0-alpha.20, a community moderator can feature or unfeature posts in other communities through federated CollectionAdd and CollectionRemove activities using CollectionType::Featured. After verify_mod_action authorizes the actor against self.community(), the receive handlers in crates/apub/activities/src/community/collection_add.rs and crates/apub/activities/src/community/collection_remove.rs dereference self.object as an ApubPost and update featured_community without verifying that post.community_id equals community.id. A moderator can therefore target an unrelated post owned by another community, push it into featured feeds and listings, or undo another community's legitimate curation decision. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.20.

Affected packages

Related vulnerabilities

• CVE-2026-96398 Incorrect Authorization vulnerability in Drupal Webform allows Forceful Browsing. CWE-863
• CVE-2026-96384 Incorrect Authorization vulnerability in Drupal Mermaid Diagram Field allows Forceful… CWE-863
• CVE-2026-96370 Incorrect Authorization vulnerability in Drupal Webform allows Server Side Request… CWE-863
• CVE-2026-96373 Incorrect Authorization vulnerability in Drupal Webform allows Forceful Browsing. CWE-863
• CVE-2026-96366 Incorrect Authorization vulnerability in Drupal Webform allows Forceful Browsing. CWE-863
• CVE-2026-96356 Incorrect Authorization vulnerability in Drupal Webform allows Forceful Browsing. CWE-863
• CVE-2026-84917 Incorrect Authorization vulnerability in Drupal Jsonapi Role Access allows Forceful… CWE-863
• CVE-2026-84920 Incorrect Authorization vulnerability in Drupal Unpublished Node Permissions allows… CWE-863