{"id":"CVE-2020-26257","aliases":["ALPINE-CVE-2020-26257","DEBIAN-CVE-2020-26257","EUVD-2020-0106","GHSA-hxmp-pqch-c8mm","PYSEC-2020-236","UBUNTU-CVE-2020-26257","openSUSE-SU-2024:11041-1"],"status":"published","title":"Denial of service attack via incorrect parameters to federation APIs","description":"Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference \"homeserver\" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","severity":{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.02392,"percentile":0.84088,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-400","CWE-74","CWE-79"],"published":"2020-12-09T18:21:29Z","modified":"2026-11-03T06:32:37Z","fixes":[{"ecosystem":"PyPI","package":"matrix-synapse","fixed_in":["1.23.1"],"sources":["ghsa","osv"]},{"ecosystem":"Alpine:v3.13","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.14","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.15","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.16","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.17","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.18","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.19","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.20","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.21","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.22","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.23","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.24","package":"synapse","fixed_in":["1.24.0-r0"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"matrix-synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.23.1"}]}]},{"source":"osv","ecosystem":"Alpine:v3.13","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.14","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.15","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.16","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.17","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.18","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.19","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.20","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.21","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.22","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.23","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.24","package":"synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.0-r0"}]}]},{"source":"osv","ecosystem":"PyPI","package":"matrix-synapse","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.23.1"}]}],"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","1.3.0","1.3.0rc1","1.3.1","1.4.0","1.4.0rc1","1.4.0rc2","1.4.1","1.4.1rc1","1.5.0","1.5.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Party Advisory","advisory","web","report"]},{"url":"https://github.com/matrix-org/synapse/pull/8776","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web","report"]},{"url":"https://github.com/matrix-org/synapse/commit/3ce2f303f15f6ac3dc352298972dc6e04d9b7a8b","tags":["x_refsource_MISC","x_transferred","Patch","Third Party Advisory","fix","web","report"]},{"url":"https://github.com/matrix-org/synapse/blob/develop/CHANGES.md#synapse-1231-2020-12-09","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/QR4MMYZKX5N5GYGH4H5LBUUC5TLAFHI7/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred","web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DBTIU3ZNBFWZ56V4X7JIAD33V5H2GOMC/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-26257","tags":["advisory"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/matrix-synapse/PYSEC-2020-236.yaml","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DBTIU3ZNBFWZ56V4X7JIAD33V5H2GOMC","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QR4MMYZKX5N5GYGH4H5LBUUC5TLAFHI7","tags":["web"]},{"url":"https://github.com/advisories/GHSA-hxmp-pqch-c8mm"},{"url":"https://security.alpinelinux.org/vuln/CVE-2020-26257","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2020-26257","tags":["advisory"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/QR4MMYZKX5N5GYGH4H5LBUUC5TLAFHI7/","tags":["web"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DBTIU3ZNBFWZ56V4X7JIAD33V5H2GOMC/","tags":["web"]},{"url":"https://ubuntu.com/security/CVE-2020-26257","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2020-26257","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-2020-26257","title":"Denial of service attack via incorrect parameters to federation APIs","description":"Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference \"homeserver\" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"published","published":"2020-12-09T18:25:15Z","modified":"2024-08-04T15:56:03.561Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"cna"}],"cwes":["CWE-400","CWE-79"],"updated_at":"2026-11-02T14:35:46.129376Z"}],"euvd":[{"id":"EUVD-2020-0106","description":"Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference \"homeserver\" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"published","published":"2020-12-09T18:25:15Z","modified":"2024-08-04T15:56:03Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"updated_at":"2026-11-03T03:07:15.778249Z"}],"ghsa":[{"id":"GHSA-hxmp-pqch-c8mm","title":"Denial of service attack via incorrect parameters in Matrix Synapse","description":"### Impact\n\nA malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request.\n\nThis can lead to a denial of service in which future events will not be correctly sent to other servers over federation.\n\nThis affects any server which accepts federation requests from untrusted servers.\n\n### Patches\n\nIssue is resolved by https://github.com/matrix-org/synapse/pull/8776.\n\n### Workarounds\n\nHomeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"published","published":"2020-12-09T18:21:29Z","modified":"2024-09-24T17:44:51Z","cvss":[{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"cwes":["CWE-74","CWE-79","CWE-400"],"updated_at":"2026-11-02T14:38:05.526697Z"}],"nvd":[{"id":"CVE-2020-26257","description":"Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference \"homeserver\" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"published","published":"2020-12-09T19:15:11.5Z","modified":"2026-06-17T03:07:56.21Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"secondary"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium","assessor":"primary"},{"version":"2.0","score":4,"vector":"AV:N/AC:L/Au:S/C:N/I:N/A:P","level":"medium","assessor":"primary"}],"cwes":["CWE-79","CWE-400"],"updated_at":"2026-11-02T14:06:27.10541Z"}],"osv":[{"id":"ALPINE-CVE-2020-26257","description":"Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference \"homeserver\" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"published","published":"2020-12-09T19:15:11.5Z","modified":"2026-11-03T06:32:37.051248178Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"updated_at":"2026-11-03T07:17:20.312441Z"},{"id":"CVE-2020-26257","description":"Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference \"homeserver\" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"published","published":"2020-12-09T19:15:11.5Z","modified":"2026-10-20T10:52:56.248551485Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"updated_at":"2026-11-02T15:44:15.879068Z"},{"id":"DEBIAN-CVE-2020-26257","description":"Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference \"homeserver\" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"withdrawn","published":"2020-12-09T19:15:11.5Z","modified":"2026-08-11T20:49:50.333742923Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"updated_at":"2026-11-02T15:45:33.729655Z"},{"id":"GHSA-hxmp-pqch-c8mm","title":"Denial of service attack via incorrect parameters in Matrix Synapse","description":"### Impact\n\nA malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request.\n\nThis can lead to a denial of service in which future events will not be correctly sent to other servers over federation.\n\nThis affects any server which accepts federation requests from untrusted servers.\n\n### Patches\n\nIssue is resolved by https://github.com/matrix-org/synapse/pull/8776.\n\n### Workarounds\n\nHomeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"published","published":"2020-12-09T18:21:29Z","modified":"2026-09-10T03:49:00.422107261Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"},{"version":"4.0","score":7.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","level":"high"}],"cwes":["CWE-400","CWE-74","CWE-79"],"updated_at":"2026-11-02T15:46:49.621585Z"},{"id":"UBUNTU-CVE-2020-26257","description":"Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference \"homeserver\" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"published","published":"2020-12-09T19:15:00Z","modified":"2025-10-24T04:48:47Z","cvss":[{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","level":"medium"}],"updated_at":"2026-11-02T15:54:23.905183Z"},{"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-2020-236","description":"Matrix is an ecosystem for open federated Instant Messaging and VoIP. Synapse is a reference \"homeserver\" implementation of Matrix. A malicious or poorly-implemented homeserver can inject malformed events into a room by specifying a different room id in the path of a `/send_join`, `/send_leave`, `/invite` or `/exchange_third_party_invite` request. This can lead to a denial of service in which future events will not be correctly sent to other servers over federation. This affects any server which accepts federation requests from untrusted servers. The Matrix Synapse reference implementation before version 1.23.1 the implementation is vulnerable to this injection attack. Issue is fixed in version 1.23.1. As a workaround homeserver administrators could limit access to the federation API to trusted servers (for example via `federation_domain_whitelist`).","status":"published","published":"2020-12-09T19:15:00Z","modified":"2023-11-08T04:03:16.626703Z","updated_at":"2026-11-02T15:52:52.192131Z"}]}}