{"id":"CVE-2021-32659","state":"PUBLISHED","title":"Automatic room upgrade handling can be used maliciously to bridge a room non-consentually","description":"Matrix-appservice-bridge is the bridging service for the Matrix communication program's application services. In versions 2.6.0 and earlier, if a bridge has room upgrade handling turned on in the configuration (the `roomUpgradeOpts` key when instantiating a new `Bridge` instance.), any `m.room.tombstone` event it encounters will be used to unbridge the current room and bridge into the target room. However, the target room `m.room.create` event is not checked to verify if the `predecessor` field contains the previous room. This means that any malicious admin of a bridged room can repoint the traffic to a different room without the new room being aware. Versions 2.6.1 and greater are patched. As a workaround, disabling the automatic room upgrade handling can be done by removing the `roomUpgradeOpts` key from the `Bridge` class options.","publishedAt":"2021-06-16T18:45:11.000Z","updatedAt":"2024-08-03T23:25:31.074Z","severity":{"score":6.5,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["matrix-org matrix-appservice-bridge"],"affected":[{"vendor":"matrix-org","product":"matrix-appservice-bridge","versions":[{"version":"< 2.6.1","status":"affected"}]}],"references":["https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx","https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f","https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1"],"weaknesses":["CWE-306"],"ingestedAt":"2026-10-29T19:48:33.225Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/32xxx/CVE-2021-32659.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.1","cveMetadata":{"cveId":"CVE-2021-32659","state":"PUBLISHED","datePublished":"2021-06-16T18:45:11.000Z","dateUpdated":"2024-08-03T23:25:31.074Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2021-05-12T00:00:00.000Z"},"containers":{"cna":{"title":"Automatic room upgrade handling can be used maliciously to bridge a room non-consentually","descriptions":[{"lang":"en","value":"Matrix-appservice-bridge is the bridging service for the Matrix communication program's application services. In versions 2.6.0 and earlier, if a bridge has room upgrade handling turned on in the configuration (the `roomUpgradeOpts` key when instantiating a new `Bridge` instance.), any `m.room.tombstone` event it encounters will be used to unbridge the current room and bridge into the target room. However, the target room `m.room.create` event is not checked to verify if the `predecessor` field contains the previous room. This means that any malicious admin of a bridged room can repoint the traffic to a different room without the new room being aware. Versions 2.6.1 and greater are patched. As a workaround, disabling the automatic room upgrade handling can be done by removing the `roomUpgradeOpts` key from the `Bridge` class options."}],"affected":[{"vendor":"matrix-org","product":"matrix-appservice-bridge","versions":[{"version":"< 2.6.1","status":"affected"}]}],"references":[{"url":"https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f","tags":["x_refsource_MISC"]},{"url":"https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":6.5,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"NONE","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-306","description":"CWE-306: Missing Authentication for Critical Function","lang":"en","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","dateUpdated":"2021-06-16T18:45:11.000Z","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa"},"source":{"advisory":"GHSA-35g4-qx3c-vjhx","discovery":"UNKNOWN"},"x_legacyV4Record":{"CVE_data_meta":{"ASSIGNER":"security-advisories@github.com","ID":"CVE-2021-32659","STATE":"PUBLIC","TITLE":"Automatic room upgrade handling can be used maliciously to bridge a room non-consentually"},"affects":{"vendor":{"vendor_data":[{"product":{"product_data":[{"product_name":"matrix-appservice-bridge","version":{"version_data":[{"version_value":"< 2.6.1"}]}}]},"vendor_name":"matrix-org"}]}},"data_format":"MITRE","data_type":"CVE","data_version":"4.0","description":{"description_data":[{"lang":"eng","value":"Matrix-appservice-bridge is the bridging service for the Matrix communication program's application services. In versions 2.6.0 and earlier, if a bridge has room upgrade handling turned on in the configuration (the `roomUpgradeOpts` key when instantiating a new `Bridge` instance.), any `m.room.tombstone` event it encounters will be used to unbridge the current room and bridge into the target room. However, the target room `m.room.create` event is not checked to verify if the `predecessor` field contains the previous room. This means that any malicious admin of a bridged room can repoint the traffic to a different room without the new room being aware. Versions 2.6.1 and greater are patched. As a workaround, disabling the automatic room upgrade handling can be done by removing the `roomUpgradeOpts` key from the `Bridge` class options."}]},"impact":{"cvss":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":6.5,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"NONE","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","version":"3.1"}},"problemtype":{"problemtype_data":[{"description":[{"lang":"eng","value":"CWE-306: Missing Authentication for Critical Function"}]}]},"references":{"reference_data":[{"name":"https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx","refsource":"CONFIRM","url":"https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx"},{"name":"https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f","refsource":"MISC","url":"https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f"},{"name":"https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1","refsource":"MISC","url":"https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1"}]},"source":{"advisory":"GHSA-35g4-qx3c-vjhx","discovery":"UNKNOWN"}}},"adp":[{"title":"CVE Program Container","references":[{"url":"https://github.com/matrix-org/matrix-appservice-bridge/security/advisories/GHSA-35g4-qx3c-vjhx","tags":["x_refsource_CONFIRM","x_transferred"]},{"url":"https://github.com/matrix-org/matrix-appservice-bridge/commit/b69e745584a34fcfd858df33e4631e420da07b9f","tags":["x_refsource_MISC","x_transferred"]},{"url":"https://github.com/matrix-org/matrix-appservice-bridge/releases/tag/2.6.1","tags":["x_refsource_MISC","x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-03T23:25:31.074Z"}}]}}}