CyberRota Analysis
AI-GeneratedLemmy's forum platform is vulnerable to a privilege escalation issue where lower-ranked moderators can remove higher-ranked moderators from the community by exploiting a flaw in the ActivityPub protocol handling. This allows unauthorized changes to moderator roles, potentially destabilizing community governance and trust. Administrators of Lemmy instances running versions prior to 0.19.19 and 1.0.0-alpha.18 should prioritize updating to mitigate this risk.
Public Exploit Signal
A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.
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Original NVD Description
Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, a lower-ranked remote moderator can remove a higher-ranked moderator by sending a signed ActivityPub Remove activity to the target instance. The local API uses LocalUser::is_higher_mod_or_admin_check to enforce moderator rank, but CollectionRemove::verify in crates/apub/activities/src/community/collection_remove.rs only calls verify_mod_action. CollectionRemove::receive dereferences self.object as an ApubPerson, creates a CommunityModeratorForm, and calls CommunityActions::leave without checking that the actor outranks the moderator identified by the object field. In communities with federated moderators, a junior moderator can therefore strip senior moderators from the community moderator list even though the local API rejects the same action. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.18.