Vulnerability Description
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.
Related Weaknesses (CWE)
References
- https://github.com/LemmyNet/lemmy/commit/108d78c592cc88bac2b0bf52ca6631be54f6fb2
- https://github.com/LemmyNet/lemmy/commit/abe256243822526dcd4bca857f7c0adeb49944f
- https://github.com/LemmyNet/lemmy/pull/6500
- https://github.com/LemmyNet/lemmy/pull/6501
- https://github.com/LemmyNet/lemmy/releases/tag/0.19.19
- https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.20
- https://github.com/LemmyNet/lemmy/security/advisories/GHSA-gwfj-h8r7-792v
- https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19
- https://github.com/LemmyNet/lemmy/security/advisories/GHSA-gwfj-h8r7-792v
FAQ
What is CVE-2026-54742?
CVE-2026-54742 is a documented vulnerability. 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 Colle...
How severe is CVE-2026-54742?
CVSS scoring is not yet available for CVE-2026-54742. Check NVD for updates.
Is there a patch for CVE-2026-54742?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.