{"id":"CVE-2021-41281","aliases":["ALPINE-CVE-2021-41281","DEBIAN-CVE-2021-41281","EUVD-2021-0133","GHSA-3hfw-x7gx-437c","PYSEC-2021-436","UBUNTU-CVE-2021-41281","openSUSE-SU-2024:11649-1"],"status":"published","title":"Path traversal in Matrix Synapse","description":"Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected, since Synapse will check the remote hostname, including the trailing `../`s, against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could, at the expense of losing media functionality, may block the certain endpoints as a workaround. Alternatively, non-containerized deployments can be adapted to use the hardened systemd config.","severity":{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-10","score":0.01577,"percentile":0.75682,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-22"],"published":"2021-11-23T19:15:18Z","modified":"2026-11-03T06:32:47Z","fixes":[{"ecosystem":"PyPI","package":"matrix-synapse","fixed_in":["1.47.1"],"sources":["ghsa","osv"]},{"ecosystem":"Alpine:v3.15","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.16","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.17","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.18","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.19","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.20","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.21","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.22","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.23","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.24","package":"synapse","fixed_in":["1.47.1-r0"],"sources":["osv"]},{"ecosystem":"openSUSE:Tumbleweed","package":"matrix-synapse","fixed_in":["1.47.1-1.1"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"matrix-synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1"}]}]},{"source":"osv","ecosystem":"Alpine:v3.15","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.16","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.17","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.18","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.19","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.20","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.21","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.22","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.23","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.24","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1-r0"}]}]},{"source":"osv","ecosystem":"PyPI","package":"matrix-synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.47.1"}]}],"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","1.33.1","1.33.2","1.34.0","1.34.0rc1","1.35.0","1.35.0rc1","1.35.0rc2","1.35.0rc3","1.35.1","1.36.0","1.36.0rc1","1.36.0rc2","1.37.0","1.37.0rc1","1.37.1","1.37.1rc1","1.38.0","1.38.0rc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Party Advisory","advisory","web","report"]},{"url":"https://github.com/matrix-org/synapse/commit/91f2bd090","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web","report"]},{"url":"https://github.com/matrix-org/synapse/releases/tag/v1.47.1","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/N3WY56LCEZ4ZECLWV5KMAXF2PSMUB4F2/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred","web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EU7QRE55U4IUEDLKT5IYPWL3UXMELFAS/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-41281","tags":["advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2021-436.yaml","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/EU7QRE55U4IUEDLKT5IYPWL3UXMELFAS","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/N3WY56LCEZ4ZECLWV5KMAXF2PSMUB4F2","tags":["web"]},{"url":"https://github.com/advisories/GHSA-3hfw-x7gx-437c"},{"url":"https://security.alpinelinux.org/vuln/CVE-2021-41281","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-41281","tags":["advisory"]},{"url":"https://github.com/matrix-org/synapse","tags":["package"]},{"url":"https://ubuntu.com/security/CVE-2021-41281","tags":["report"]},{"url":"https://github.com/matrix-org/synapse/commit/91f2bd0907f1d05af67166846988e49644eb650c","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-41281","tags":["report"]},{"url":"","tags":["advisory"]},{"url":"https://www.suse.com/security/cve/CVE-2021-41281","tags":["web"]}],"sources":{"cve":[{"id":"CVE-2021-41281","title":"Path traversal in Matrix Synapse","description":"Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected, since Synapse will check the remote hostname, including the trailing `../`s, against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could, at the expense of losing media functionality, may block the certain endpoints as a workaround. Alternatively, non-containerized deployments can be adapted to use the hardened systemd config.","status":"published","published":"2021-11-23T19:15:18Z","modified":"2024-08-04T03:08:31.942Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"cna"}],"cwes":["CWE-22"],"updated_at":"2026-11-02T14:32:59.105382Z"}],"euvd":[{"id":"EUVD-2021-0133","description":"Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected, since Synapse will check the remote hostname, including the trailing `../`s, against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could, at the expense of losing media functionality, may block the certain endpoints as a workaround. Alternatively, non-containerized deployments can be adapted to use the hardened systemd config.","status":"published","published":"2021-11-23T19:15:18Z","modified":"2024-08-04T03:08:31Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"updated_at":"2026-11-03T03:24:18.784846Z"}],"ghsa":[{"id":"GHSA-3hfw-x7gx-437c","title":"Path traversal in Matrix Synapse","description":"### Impact\n\nSynapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory, potentially outside the media store directory.\n\nThe last two directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact.\n\nHomeservers with the media repository disabled are unaffected. Homeservers configured with a federation whitelist are also unaffected.\n\n### Patches\nServer administrators should upgrade to 1.47.1 or later.\n\n### Workarounds\nServer administrators using a reverse proxy could, at the expense of losing media functionality, block the following endpoints:\n\n* `/_matrix/media/r0/download/{serverName}/{mediaId}`\n* `/_matrix/media/r0/download/{serverName}/{mediaId}/{fileName}`\n* `/_matrix/media/r0/thumbnail/{serverName}/{mediaId}`\n\nAlternatively, non-containerized deployments can be adapted to use the hardened systemd config, located at `contrib/systemd/override-hardened.conf`.\n\n### References\nn/a\n\n### For more information\n\nIf you have any questions or comments about this advisory, e-mail us at security@matrix.org.\n","status":"published","published":"2021-11-23T21:58:56Z","modified":"2024-09-24T15:47:20Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"},{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-22"],"updated_at":"2026-11-02T14:38:05.526697Z"}],"nvd":[{"id":"CVE-2021-41281","description":"Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected, since Synapse will check the remote hostname, including the trailing `../`s, against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could, at the expense of losing media functionality, may block the certain endpoints as a workaround. Alternatively, non-containerized deployments can be adapted to use the hardened systemd config.","status":"published","published":"2021-11-23T20:15:11.687Z","modified":"2026-06-17T04:08:14.11Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high","assessor":"secondary"},{"version":"2.0","score":4.3,"vector":"AV:N/AC:M/Au:N/C:N/I:P/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-22"],"updated_at":"2026-11-02T14:07:01.428028Z"}],"osv":[{"id":"ALPINE-CVE-2021-41281","description":"Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected, since Synapse will check the remote hostname, including the trailing `../`s, against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could, at the expense of losing media functionality, may block the certain endpoints as a workaround. Alternatively, non-containerized deployments can be adapted to use the hardened systemd config.","status":"published","published":"2021-11-23T20:15:11.687Z","modified":"2026-11-03T06:32:47.836775025Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"updated_at":"2026-11-03T07:16:46.202932Z"},{"id":"CVE-2021-41281","description":"Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected, since Synapse will check the remote hostname, including the trailing `../`s, against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could, at the expense of losing media functionality, may block the certain endpoints as a workaround. Alternatively, non-containerized deployments can be adapted to use the hardened systemd config.","status":"published","published":"2021-11-23T20:15:11.687Z","modified":"2026-10-20T10:54:58.313828385Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T15:44:21.557945Z"},{"id":"DEBIAN-CVE-2021-41281","description":"Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected, since Synapse will check the remote hostname, including the trailing `../`s, against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could, at the expense of losing media functionality, may block the certain endpoints as a workaround. Alternatively, non-containerized deployments can be adapted to use the hardened systemd config.","status":"withdrawn","published":"2021-11-23T20:15:11.687Z","modified":"2026-08-11T20:49:48.817514663Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T15:45:35.521549Z"},{"id":"GHSA-3hfw-x7gx-437c","title":"Path traversal in Matrix Synapse","description":"### Impact\n\nSynapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory, potentially outside the media store directory.\n\nThe last two directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact.\n\nHomeservers with the media repository disabled are unaffected. Homeservers configured with a federation whitelist are also unaffected.\n\n### Patches\nServer administrators should upgrade to 1.47.1 or later.\n\n### Workarounds\nServer administrators using a reverse proxy could, at the expense of losing media functionality, block the following endpoints:\n\n* `/_matrix/media/r0/download/{serverName}/{mediaId}`\n* `/_matrix/media/r0/download/{serverName}/{mediaId}/{fileName}`\n* `/_matrix/media/r0/thumbnail/{serverName}/{mediaId}`\n\nAlternatively, non-containerized deployments can be adapted to use the hardened systemd config, located at `contrib/systemd/override-hardened.conf`.\n\n### References\nn/a\n\n### For more information\n\nIf you have any questions or comments about this advisory, e-mail us at security@matrix.org.\n","status":"published","published":"2021-11-23T21:58:56Z","modified":"2026-07-08T06:28:00.355576319Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"},{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-22"],"updated_at":"2026-11-02T15:46:35.747385Z"},{"id":"UBUNTU-CVE-2021-41281","description":"Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected, since Synapse will check the remote hostname, including the trailing `../`s, against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could, at the expense of losing media functionality, may block the certain endpoints as a workaround. Alternatively, non-containerized deployments can be adapted to use the hardened systemd config.","status":"published","published":"2021-11-23T20:15:00Z","modified":"2025-10-24T04:50:35Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T15:54:29.220315Z"},{"id":"openSUSE-SU-2024:11649-1","title":"matrix-synapse-1.47.1-1.1 on GA media","description":"These are all security issues fixed in the matrix-synapse-1.47.1-1.1 package on the GA media of openSUSE Tumbleweed.","status":"published","published":"2024-06-15T00:00:00Z","modified":"2026-02-04T02:41:16.281516Z","updated_at":"2026-11-02T16:58:35.195147Z"},{"id":"PYSEC-2021-436","description":"Synapse is a package for Matrix homeservers written in Python 3/Twisted. Prior to version 1.47.1, Synapse instances with the media repository enabled can be tricked into downloading a file from a remote server into an arbitrary directory. No authentication is required for the affected endpoint. The last 2 directories and file name of the path are chosen randomly by Synapse and cannot be controlled by an attacker, which limits the impact. Homeservers with the media repository disabled are unaffected. Homeservers with a federation whitelist are also unaffected, since Synapse will check the remote hostname, including the trailing `../`s, against the whitelist. Server administrators should upgrade to 1.47.1 or later. Server administrators using a reverse proxy could, at the expense of losing media functionality, may block the certain endpoints as a workaround. Alternatively, non-containerized deployments can be adapted to use the hardened systemd config.","status":"published","published":"2021-11-23T20:15:00Z","modified":"2026-02-26T23:27:06.31956Z","updated_at":"2026-11-02T15:52:53.119977Z"}]}}