{"apiVersion":"1.0","identifier":"CVE-2026-54742","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.","publishedAt":"2026-08-19T20:17:17","lastModifiedAt":"2026-08-20T20:17:35","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-54742","cvssScore":5.1,"cvssVector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","epssProbability":0.00419,"riskScore":0.53,"affectedProduct":"Lemmy","affectedVersions":">=0.19.18,<0.19.19,>=1.0.0-alpha.20,<1.0.0-alpha.20","vulnerabilityType":"Web app","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-54742","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-54742","en":"https://www.redsauce.net/en/cves/CVE-2026-54742","fr":"https://www.redsauce.net/fr/cves/CVE-2026-54742","pt":"https://www.redsauce.net/pt/cves/CVE-2026-54742","de":"https://www.redsauce.net/de/cves/CVE-2026-54742","sk":"https://www.redsauce.net/sk/cves/CVE-2026-54742","el":"https://www.redsauce.net/el/cves/CVE-2026-54742"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-54742"}}