{"id":"CVE-2021-39163","aliases":["ALPINE-CVE-2021-39163","DEBIAN-CVE-2021-39163","EUVD-2021-0131","GHSA-jj53-8fmw-f2w2","PYSEC-2021-424","UBUNTU-CVE-2021-39163","openSUSE-SU-2024:11041-1"],"status":"published","title":"Adding a private/unlisted room to a community exposes room metadata in an unauthorised manner.","description":"Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.","severity":{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00896,"percentile":0.60041,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-200","CWE-863"],"published":"2021-08-31T16:00:11Z","modified":"2026-11-03T06:32:58Z","fixes":[{"ecosystem":"PyPI","package":"matrix-synapse","fixed_in":["1.41.1"],"sources":["ghsa","osv"]},{"ecosystem":"Alpine:v3.14","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.15","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.16","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.17","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.18","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.19","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.20","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.21","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.22","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.23","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.24","package":"synapse","fixed_in":["1.41.1-r0"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"matrix-synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1"}]}]},{"source":"osv","ecosystem":"Alpine:v3.14","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.15","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.16","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.17","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.18","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.19","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.20","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.21","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.22","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.23","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.24","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1-r0"}]}]},{"source":"osv","ecosystem":"PyPI","package":"matrix-synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.41.1"}]}],"versions":["0.33.5","0.33.5.1","0.33.6","0.33.6rc1","0.33.7","0.33.7rc1","0.33.7rc2","0.33.8","0.33.8rc2","0.33.9","0.34.0","0.34.0.1","0.34.0rc1","0.34.0rc2","0.34.1.1","0.99.0","0.99.0rc1","0.99.0rc2","0.99.0rc3","0.99.0rc4","0.99.1","0.99.1.1","0.99.1rc1","0.99.1rc2","0.99.2","0.99.2rc1","0.99.3","0.99.3.1","0.99.3.2","0.99.3rc1","0.99.4","0.99.4rc1","0.99.5","0.99.5.1","0.99.5.2","0.99.5rc1","1.0.0","1.0.0rc1","1.0.0rc2","1.0.0rc3","1.1.0","1.1.0rc1","1.1.0rc2","1.10.0","1.10.0rc1","1.10.0rc2","1.10.0rc3","1.10.0rc5","1.10.1","1.11.0","1.11.0rc1","1.11.1","1.12.0","1.12.0rc1","1.12.1","1.12.1rc1","1.12.2","1.12.3","1.12.4","1.12.4rc1","1.13.0","1.13.0rc1","1.13.0rc2","1.13.0rc3","1.14.0","1.14.0rc1","1.14.0rc2","1.15.0","1.15.0rc1","1.15.1","1.15.2","1.16.0","1.16.0rc1","1.16.0rc2","1.16.1","1.17.0","1.17.0rc1","1.18.0","1.18.0rc1","1.18.0rc2","1.19.0","1.19.0rc1","1.19.1","1.19.1rc1","1.19.2","1.19.3","1.2.0","1.2.0rc1","1.2.0rc2","1.2.1","1.20.0","1.20.0rc1","1.20.0rc2","1.20.0rc3","1.20.0rc4","1.20.0rc5","1.20.1","1.21.0","1.21.0rc1","1.21.0rc2","1.21.0rc3","1.21.1","1.21.2","1.22.0","1.22.0rc1","1.22.0rc2","1.22.1","1.23.0","1.23.0rc1","1.23.1","1.24.0","1.24.0rc1","1.24.0rc2","1.25.0","1.25.0rc1","1.26.0","1.26.0rc1","1.26.0rc2","1.27.0","1.27.0rc1","1.27.0rc2","1.28.0","1.28.0rc1","1.29.0","1.29.0rc1","1.3.0","1.3.0rc1","1.3.1","1.30.0","1.30.0rc1","1.30.1","1.31.0","1.31.0rc1","1.32.0","1.32.0rc1","1.32.1","1.32.2","1.33.0","1.33.0rc1","1.33.0rc2"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Party Advisory","advisory","web","report"]},{"url":"https://github.com/matrix-org/synapse/commit/cb35df940a","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web","report"]},{"url":"https://github.com/matrix-org/synapse/releases/tag/v1.41.1","tags":["x_refsource_MISC","x_transferred","Release Notes","Third Party Advisory","advisory","web","report"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PXT7ID7DNBRN2TVTETU3SYQHJKEG6PXN/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred","web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2VHDEPCZ22GJFMZCWA2XZAGPOEV72POF/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-39163","tags":["advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-424.yaml","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2VHDEPCZ22GJFMZCWA2XZAGPOEV72POF","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PXT7ID7DNBRN2TVTETU3SYQHJKEG6PXN","tags":["web"]},{"url":"https://github.com/advisories/GHSA-jj53-8fmw-f2w2"},{"url":"https://security.alpinelinux.org/vuln/CVE-2021-39163","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-39163","tags":["advisory"]},{"url":"https://github.com/matrix-org/synapse","tags":["package"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PXT7ID7DNBRN2TVTETU3SYQHJKEG6PXN/","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2VHDEPCZ22GJFMZCWA2XZAGPOEV72POF/","tags":["web"]},{"url":"https://ubuntu.com/security/CVE-2021-39163","tags":["report"]},{"url":"https://github.com/matrix-org/synapse/commit/cb35df940a828bc40b96daed997b5ad4c7842fd3","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-39163","tags":["report"]},{"url":"","tags":["advisory"]},{"url":"https://www.suse.com/security/cve/CVE-2018-12291","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2019-5885","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2020-10108","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2020-10109","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2020-1971","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2020-26257","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2020-26891","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2021-29471","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2021-3449","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2021-39163","tags":["web"]},{"url":"https://www.suse.com/security/cve/CVE-2021-39164","tags":["web"]}],"sources":{"cve":[{"id":"CVE-2021-39163","title":"Adding a private/unlisted room to a community exposes room metadata in an unauthorised manner.","description":"Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.","status":"published","published":"2021-08-31T16:00:11Z","modified":"2024-08-04T01:58:18.227Z","cvss":[{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"cna"}],"cwes":["CWE-200"],"updated_at":"2026-11-02T14:33:09.175141Z"}],"euvd":[{"id":"EUVD-2021-0131","description":"Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.","status":"published","published":"2021-08-31T16:00:11Z","modified":"2024-08-04T01:58:18Z","cvss":[{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"updated_at":"2026-11-03T03:24:24.305495Z"}],"ghsa":[{"id":"GHSA-jj53-8fmw-f2w2","title":"Adding a private/unlisted room to a community exposes room metadata in an unauthorised manner.","description":"### Impact\nUnauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where:\n- the vulnerable homeserver is in the room; and\n- untrusted users are permitted to create groups (communities).\n\nBy default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted.\n\n### Patches\nServer administrators should upgrade to 1.41.1 or higher.\n\n### Workarounds\nServer administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators.\n\nAdministrators that are using a reverse proxy could, with partial loss of group functionality, block the following endpoints:\n* `/_matrix/client/r0/groups/{group_id}/rooms`\n* `/_matrix/client/unstable/groups/{group_id}/rooms`\n\n### References\nn/a\n\n### For more information\nIf you have any questions or comments about this advisory, e-mail us at security@matrix.org.\n","status":"published","published":"2021-09-01T18:25:44Z","modified":"2024-09-24T15:37:58Z","cvss":[{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","level":"low"},{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"cwes":["CWE-200"],"updated_at":"2026-11-02T14:38:05.526697Z"}],"nvd":[{"id":"CVE-2021-39163","description":"Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.","status":"published","published":"2021-08-31T16:15:07.95Z","modified":"2026-06-17T04:03:13.563Z","cvss":[{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"secondary"},{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low","assessor":"primary"},{"version":"2.0","score":3.5,"vector":"AV:N/AC:M/Au:S/C:P/I:N/A:N","level":"low","assessor":"primary"}],"cwes":["CWE-200","CWE-863"],"updated_at":"2026-11-02T14:06:57.67549Z"}],"osv":[{"id":"ALPINE-CVE-2021-39163","description":"Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.","status":"published","published":"2021-08-31T16:15:07.95Z","modified":"2026-11-03T06:32:58.584088355Z","cvss":[{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"updated_at":"2026-11-03T07:16:09.603409Z"},{"id":"CVE-2021-39163","description":"Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.","status":"published","published":"2021-08-31T16:15:07.95Z","modified":"2026-10-20T10:54:53.175356049Z","cvss":[{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"updated_at":"2026-11-02T15:44:20.843843Z"},{"id":"DEBIAN-CVE-2021-39163","description":"Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.","status":"withdrawn","published":"2021-08-31T16:15:07.95Z","modified":"2026-08-11T20:49:52.86251295Z","cvss":[{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"updated_at":"2026-11-02T15:45:35.521549Z"},{"id":"GHSA-jj53-8fmw-f2w2","title":"Adding a private/unlisted room to a community exposes room metadata in an unauthorised manner.","description":"### Impact\nUnauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where:\n- the vulnerable homeserver is in the room; and\n- untrusted users are permitted to create groups (communities).\n\nBy default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted.\n\n### Patches\nServer administrators should upgrade to 1.41.1 or higher.\n\n### Workarounds\nServer administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators.\n\nAdministrators that are using a reverse proxy could, with partial loss of group functionality, block the following endpoints:\n* `/_matrix/client/r0/groups/{group_id}/rooms`\n* `/_matrix/client/unstable/groups/{group_id}/rooms`\n\n### References\nn/a\n\n### For more information\nIf you have any questions or comments about this advisory, e-mail us at security@matrix.org.\n","status":"published","published":"2021-09-01T18:25:44Z","modified":"2026-07-08T06:29:05.866083195Z","cvss":[{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low"},{"version":"4.0","score":2.3,"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","level":"low"}],"cwes":["CWE-200"],"updated_at":"2026-11-02T15:46:50.687609Z"},{"id":"UBUNTU-CVE-2021-39163","description":"Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.","status":"published","published":"2021-08-31T16:15:00Z","modified":"2025-10-24T04:50:29Z","cvss":[{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low"},{"version":"3.1","score":3.1,"vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N","level":"low"}],"updated_at":"2026-11-02T15:54:28.526929Z"},{"id":"openSUSE-SU-2024:11041-1","title":"matrix-synapse-1.43.0-1.1 on GA media","description":"These are all security issues fixed in the matrix-synapse-1.43.0-1.1 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2024-06-15T00:00:00Z","modified":"2026-02-04T03:22:36.180382Z","updated_at":"2026-11-02T16:58:34.894275Z"},{"id":"PYSEC-2021-424","description":"Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators that are using a reverse proxy could, with partial loss of group functionality, block the endpoints `/_matrix/client/r0/groups/{group_id}/rooms` and `/_matrix/client/unstable/groups/{group_id}/rooms`.","status":"published","published":"2021-08-31T16:15:00Z","modified":"2026-02-26T23:24:55.705814Z","updated_at":"2026-11-02T15:52:53.119977Z"}]}}