CVE-2026-54740

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{"affected": [{"affectedData": [{"product": "lemmy", "vendor": "LemmyNet", "versions": [{"status": "affected", "version": "< 0.19.19"}, {"status": "affected", "version": ">= 1.0.0-alpha.0, < 1.0.0-alpha.18"}]}], "source": "security-advisories@github.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2026-54740", "lastModified": "2026-09-09T21:15:59.613", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.6, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-54740", "options": [{"exploitation": "poc"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-08-20T19:57:07.165095Z", "version": "2.0.3"}}]}, "published": "2026-08-19T21:16:58.363", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/commit/d127e714a66f34f6b9c8ea15f20097ac907cdf28"}, {"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/commit/ede1d348344ca2027fd1bc6a0cab25575c0c3a4c"}, {"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/pull/6475"}, {"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/pull/6478"}, {"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.19"}, {"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18"}, {"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xmpx-2j2f-c7g7"}, {"source": "security-advisories@github.com", "url": "https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19"}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xmpx-2j2f-c7g7"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Deferred", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-862"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{}

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