{"id":"CVE-2021-21274","published":"2021-02-26T17:25:16Z","modified":"2024-08-03T18:09:15Z","title":"Denial of service attack via .well-known lookups","vendor":"matrix-org","product":"synapse","tier":"tail","description":{"text":"Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.25.0, a malicious homeserver could redirect requests to their .well-known file to a large file. This can lead to a denial of service attack where homeservers will consume significantly more resources when requesting the .well-known file of a malicious homeserver. This affects any server which accepts federation requests from untrusted servers. Issue is resolved in version 1.25.0. As a workaround the `federation_domain_whitelist` setting can be used to restrict the homeservers communicated with over federation.","provenance":"source","from":"CVE.org"},"cvss":{"score":4.3,"severity":"MEDIUM","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","provenance":"source","from":"CVE.org CNA"},"epss":{"score":0.02164,"percentile":0.82187,"provenance":"source"},"cwes":[{"id":"CWE-400","name":"Uncontrolled Resource Consumption"}],"references":[{"url":"https://github.com/matrix-org/synapse/security/advisories/GHSA-2hwx-mjrm-v3g8","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/matrix-org/synapse/releases/tag/v1.25.0","tags":["x_refsource_MISC"]},{"url":"https://github.com/matrix-org/synapse/pull/8950","tags":["x_refsource_MISC"]},{"url":"https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6","tags":["x_refsource_MISC"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TNNAJOZNMVMXM6AS7RFFKB4QLUJ4IFEY/","tags":["vendor-advisory","x_refsource_FEDORA"]}],"priority":{"score":19.4,"factors":[{"name":"EPSS percentile","points":16.44},{"name":"CVSS severity","points":3.01}]},"vendorSlug":"matrix-org","affectedVersions":[{"vendor":"matrix-org","product":"synapse","versions":[">=0.99.0, < 1.25.0"]}],"affected":[{"ecosystem":"PyPI","package":"matrix-synapse","vulnerableRanges":[">=0.99.0, <1.25.0"],"patched":["1.25.0"],"from":["GHSA-2hwx-mjrm-v3g8","PYSEC-2021-132"],"provenance":"source"}],"euvd":{"id":"EUVD-2021-0124","exploited":false,"provenance":"source"},"lineage":{"familyId":"fam-matrix-org-synapse-cve-2019-18835","parents":[{"from":"CVE-2021-21273","to":"CVE-2021-21274","relation":"related","confidence":"medium","kind":"lineage","evidence":[{"kind":"same-code","provenance":"machine","files":["synapse/http/client.py","synapse/http/matrixfederationclient.py"],"commits":["https://github.com/matrix-org/synapse/commit/30fba6210834a4ecd91badf0c8f3eb278b72e746","https://github.com/matrix-org/synapse/commit/ff5c4da1289cb5e097902b3e55b771be342c29d6"],"basis":"rarely changed file"}]}],"packageHistory":[{"cve":"CVE-2020-26891","published":"2020-10-19","fixed":"1.21.0","kev":false},{"cve":"CVE-2020-26257","published":"2020-12-09","fixed":"1.23.1","kev":false,"link":{"from":"CVE-2020-26257","to":"CVE-2021-21274","relation":"successor","confidence":"medium","kind":"sequence","evidence":[{"kind":"version-step","provenance":"source","package":"PyPI:matrix-synapse","fromFixed":"1.23.1","toFixed":"1.25.0","daysApart":79},{"kind":"similar","provenance":"machine","score":0.38,"basis":"same product + CWE + description similarity"}]}},{"cve":"CVE-2021-21273","published":"2021-02-26","fixed":"1.25.0","kev":false},{"cve":"CVE-2021-21274","published":"2021-02-26","fixed":"1.25.0","kev":false},{"cve":"CVE-2021-21332","published":"2021-03-26","fixed":"1.27.0","kev":false,"link":{"from":"CVE-2021-21274","to":"CVE-2021-21332","relation":"successor","confidence":"low","kind":"sequence","evidence":[{"kind":"version-step","provenance":"source","package":"PyPI:matrix-synapse","fromFixed":"1.25.0","toFixed":"1.27.0","daysApart":28}]}},{"cve":"CVE-2021-21333","published":"2021-03-26","fixed":"1.27.0","kev":false,"link":{"from":"CVE-2021-21274","to":"CVE-2021-21333","relation":"successor","confidence":"low","kind":"sequence","evidence":[{"kind":"version-step","provenance":"source","package":"PyPI:matrix-synapse","fromFixed":"1.25.0","toFixed":"1.27.0","daysApart":28}]}},{"cve":"CVE-2021-21392","published":"2021-04-12","fixed":"1.28.0","kev":false}],"package":"PyPI:matrix-synapse"}}