{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-54740", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-06-15T23:07:33.233Z", "datePublished": "2026-08-19T20:14:29.391Z", "dateUpdated": "2026-08-19T20:14:29.391Z"}, "containers": {"cna": {"title": "Lemmy: Lower-ranked federated moderator can remove higher-ranked moderators", "problemTypes": [{"descriptions": [{"cweId": "CWE-862", "lang": "en", "description": "CWE-862: Missing Authorization", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"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"}}], "references": [{"name": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xmpx-2j2f-c7g7", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-xmpx-2j2f-c7g7"}, {"name": "https://github.com/LemmyNet/lemmy/pull/6475", "tags": ["x_refsource_MISC"], "url": "https://github.com/LemmyNet/lemmy/pull/6475"}, {"name": "https://github.com/LemmyNet/lemmy/pull/6478", "tags": ["x_refsource_MISC"], "url": "https://github.com/LemmyNet/lemmy/pull/6478"}, {"name": "https://github.com/LemmyNet/lemmy/commit/d127e714a66f34f6b9c8ea15f20097ac907cdf28", "tags": ["x_refsource_MISC"], "url": "https://github.com/LemmyNet/lemmy/commit/d127e714a66f34f6b9c8ea15f20097ac907cdf28"}, {"name": "https://github.com/LemmyNet/lemmy/commit/ede1d348344ca2027fd1bc6a0cab25575c0c3a4c", "tags": ["x_refsource_MISC"], "url": "https://github.com/LemmyNet/lemmy/commit/ede1d348344ca2027fd1bc6a0cab25575c0c3a4c"}, {"name": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.19", "tags": ["x_refsource_MISC"], "url": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.19"}, {"name": "https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18", "tags": ["x_refsource_MISC"], "url": "https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18"}, {"name": "https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19", "tags": ["x_refsource_MISC"], "url": "https://join-lemmy.org/news/2026-06-09_-_Lemmy_Release_v0.19.19"}], "affected": [{"vendor": "LemmyNet", "product": "lemmy", "versions": [{"version": "< 0.19.19", "status": "affected"}, {"version": ">= 1.0.0-alpha.0, < 1.0.0-alpha.18", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-08-19T20:14:29.391Z"}, "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."}], "source": {"advisory": "GHSA-xmpx-2j2f-c7g7", "discovery": "UNKNOWN"}}}}

{}

{"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": "2026-08-19T21:16:58.363", "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"}]}, "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"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-862"}], "source": "security-advisories@github.com", "type": "Primary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,0.19.19)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.0.0-alpha.0,1.0.0-alpha.18)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "lemmy", "source": "cna", "vendor": "LemmyNet"}, "product": "lemmy", "vendor": "lemmynet"}], "created": "2026-08-19T22:30:04.955152+00:00", "updated": "2026-08-19T22:30:04.955176+00:00", "vendors": ["lemmynet", "lemmynet$PRODUCT$lemmy"]}