{"id":"CVE-2026-54741","state":"PUBLISHED","title":"Lemmy: Blocked users can edit private messages sent before the block","description":"Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, Lemmy blocks new private messages from a sender after the recipient blocks that sender, but the edit path skips the same block check. create_private_message checks the recipient's block list with PersonActions::read_block before inserting a message, while edit_private_message in crates/api/api_crud/src/private_message/update.rs only checks that the caller is orig_private_message.creator_id. The update then writes new content and returns the modified PrivateMessageView without consulting the recipient's block list, allowing a blocked sender to keep changing an old message that the recipient can still see and providing a post-block harassment path. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.18.","publishedAt":"2026-08-19T20:13:05.201Z","updatedAt":"2026-08-20T13:21:16.938Z","severity":{"score":5.3,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["LemmyNet lemmy"],"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"}]}],"references":["https://github.com/LemmyNet/lemmy/security/advisories/GHSA-46g9-847m-qf8r","https://github.com/LemmyNet/lemmy/pull/6472","https://github.com/LemmyNet/lemmy/pull/6476","https://github.com/LemmyNet/lemmy/commit/051b317c9d14b91972bb372c67f319d6900beb93","https://github.com/LemmyNet/lemmy/commit/2d169d630b86b9351e4b1dca451214b741f46150","https://github.com/LemmyNet/lemmy/releases/tag/0.19.19","https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18"],"weaknesses":["CWE-862"],"ingestedAt":"2026-10-29T20:12:24.861Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/54xxx/CVE-2026-54741.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-54741","state":"PUBLISHED","datePublished":"2026-08-19T20:13:05.201Z","dateUpdated":"2026-08-20T13:21:16.938Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-06-15T23:12:41.964Z"},"containers":{"cna":{"title":"Lemmy: Blocked users can edit private messages sent before the block","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, Lemmy blocks new private messages from a sender after the recipient blocks that sender, but the edit path skips the same block check. create_private_message checks the recipient's block list with PersonActions::read_block before inserting a message, while edit_private_message in crates/api/api_crud/src/private_message/update.rs only checks that the caller is orig_private_message.creator_id. The update then writes new content and returns the modified PrivateMessageView without consulting the recipient's block list, allowing a blocked sender to keep changing an old message that the recipient can still see and providing a post-block harassment path. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.18."}],"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"}]}],"references":[{"url":"https://github.com/LemmyNet/lemmy/security/advisories/GHSA-46g9-847m-qf8r","name":"https://github.com/LemmyNet/lemmy/security/advisories/GHSA-46g9-847m-qf8r","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/LemmyNet/lemmy/pull/6472","name":"https://github.com/LemmyNet/lemmy/pull/6472","tags":["x_refsource_MISC"]},{"url":"https://github.com/LemmyNet/lemmy/pull/6476","name":"https://github.com/LemmyNet/lemmy/pull/6476","tags":["x_refsource_MISC"]},{"url":"https://github.com/LemmyNet/lemmy/commit/051b317c9d14b91972bb372c67f319d6900beb93","name":"https://github.com/LemmyNet/lemmy/commit/051b317c9d14b91972bb372c67f319d6900beb93","tags":["x_refsource_MISC"]},{"url":"https://github.com/LemmyNet/lemmy/commit/2d169d630b86b9351e4b1dca451214b741f46150","name":"https://github.com/LemmyNet/lemmy/commit/2d169d630b86b9351e4b1dca451214b741f46150","tags":["x_refsource_MISC"]},{"url":"https://github.com/LemmyNet/lemmy/releases/tag/0.19.19","name":"https://github.com/LemmyNet/lemmy/releases/tag/0.19.19","tags":["x_refsource_MISC"]},{"url":"https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18","name":"https://github.com/LemmyNet/lemmy/releases/tag/1.0.0-alpha.18","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"LOW","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"LOW","vulnAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":5.3,"baseSeverity":"MEDIUM","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-862","lang":"en","description":"CWE-862: Missing Authorization","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-19T20:13:05.201Z"},"source":{"advisory":"GHSA-46g9-847m-qf8r","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/LemmyNet/lemmy/security/advisories/GHSA-46g9-847m-qf8r","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-20T13:21:08.131078Z","id":"CVE-2026-54741","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-20T13:21:16.938Z"}}]}}}