CVE-2026-54740: CWE-862: Missing Authorization in LemmyNet lemmy
Description
CVE-2026-54740 is a missing authorization vulnerability in LemmyNet's lemmy software that allows a lower-ranked remote moderator to remove a higher-ranked moderator in federated communities. This occurs because the verification logic for moderator removal does not properly check the actor's rank against the target moderator's rank. The issue affects versions prior to 0.19.19 and 1.0.0-alpha.18 and has been fixed in those versions.
CVSS v3.1
Score 6.5medium
Affected software
LemmyNet
lemmy
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
LemmyNet's lemmy software contains a missing authorization vulnerability (CWE-862) where 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 enforces moderator rank via LocalUser::is_higher_mod_or_admin_check, but the federated removal logic in CollectionRemove::verify only calls verify_mod_action and does not check that the actor outranks the moderator identified by the object field. This allows junior moderators in federated communities to strip senior moderators from the community moderator list, bypassing local API restrictions. The vulnerability is fixed in versions 0.19.19 and 1.0.0-alpha.18.
Potential Impact
An attacker with lower moderator privileges on a federated instance can remove higher-ranked moderators from communities, potentially disrupting community moderation and governance. The vulnerability does not impact confidentiality or availability but allows unauthorized modification of moderator roles, impacting integrity.
Mitigation Recommendations
Upgrade lemmy to version 0.19.19 or later, or 1.0.0-alpha.18 or later, where this authorization issue is fixed. No other mitigation is required as the fix addresses the root cause.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-15T23:07:33.233Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a86e0f3acd9273b49838518
Added to database: 08/20/2026, 11:11:47 UTC
Last enriched: 09/11/2026, 05:17:49 UTC
Last updated: 10/05/2026, 06:48:17 UTC
Views: 76
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