5.1 MEDIUM
- CVSS version (CVSS): 4.0
- Attack Vector (AV): Network (N)
- Attack Complexity (AC): Low (L)
- Attack Requirement (AT): None (N)
- Privileges Required (PR): High (H)
- User Interaction (UI): None (N)
- Vulnerable System Impact Confidentiality (VC): None (N)
- Vulnerable System Impact Integrity (VI): Low (L)
- Vulnerable System Impact Availability (VA): None (N)
- Subsequent System Impact Confidentiality (SC): None (N)
- Subsequent System Impact Integrity (SI): None (N)
- Subsequent System Impact Availability (SA): None (N)
- Modified Attack Vector (MAV): Network (N)
- Modified Attack Complexity (MAC): Low (L)
- Modified Attack Requirement (MAT): None (N)
- Modified Privileges Required (MPR): High (H)
- Modified User Interaction (MUI): None (N)
- Modified Vulnerable System Impact Confidentiality (MVC): None (N)
- Modified Vulnerable System Impact Integrity (MVI): Low (L)
- Modified Vulnerable System Impact Availability (MVA): None (N)
- Modified Subsequent System Impact Confidentiality (MSC): Negligible (N)
- Modified Subsequent System Impact Integrity (MSI): Negligible (N)
- Modified Subsequent System Impact Availability (MSA): Negligible (N)
- Safety (S): Not Defined (X)
- Automatable (AU): Not Defined (X)
- Recovery (R): Not Defined (X)
- Value Density (V): Not Defined (X)
- Vulnerability Response Effort (RE): Not Defined (X)
- Provider Urgency (U): Not Defined (X)
- Confidentiality Req. (CR): Not Defined (X)
- Integrity Req. (IR): Not Defined (X)
- Availability Req. (AR): Not Defined (X)
- Exploit Maturity (E): Not Defined (X)
Activity log
- Created suggestion
Lemmy: `CollectionAdd::Featured` does not check the post is in the community
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.
References
-
https://github.com/LemmyNet/lemmy/security/advisories/GHSA-gwfj-h8r7-792v x_refsource_CONFIRM
-
https://github.com/LemmyNet/lemmy/pull/6500 x_refsource_MISC
-
https://github.com/LemmyNet/lemmy/pull/6501 x_refsource_MISC
-
https://github.com/LemmyNet/lemmy/releases/tag/0.19.19 x_refsource_MISC
-
https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.20 x_refsource_MISC
-
https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19 x_refsource_MISC
Affected products
- ==>= 1.0.0-alpha.0, < 1.0.0-alpha.20
- ==< 0.19.19
Matching in nixpkgs
pkgs.lemmy-ui
Web frontend for a federated link aggregator
pkgs.lemmy-help
CLI for generating vim help docs from emmylua comments
pkgs.lemmy-server
Federated link aggregator and forum
Package maintainers
-
@georgyo George Shammas <george@shamm.as>
-
@happysalada Raphael Megzari <raphael@megzari.com>
-
@billewanick Bill Ewanick <bill@ewanick.com>
-
@lucasew Lucas Eduardo Wendt <lucas59356@gmail.com>
-
@Prince213 Sizhe Zhao <prc.zhao@outlook.com>
-
@phanirithvij Phani Rithvij <phanirithvij2000@gmail.com>
-
@ethancedwards8 Ethan Carter Edwards <ethan@ethancedwards.com>
-
@eljamm Fedi Jamoussi <fedi.jamoussi@protonmail.ch>