{"id":"CVE-2023-45129","aliases":["GHSA-5chr-wjw5-3gq4","PYSEC-2023-199"],"url":"https://o3.security/vulnerability/CVE-2023-45129","summary":"matrix-synapse vulnerable to denial of service due to malicious server ACL events","details":"Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Prior to version 1.94.0, a malicious server ACL event can impact performance temporarily or permanently leading to a persistent denial of service. Homeservers running on a closed federation (which presumably do not need to use server ACLs) are not affected. Server administrators are advised to upgrade to Synapse 1.94.0 or later. As a workaround, rooms with malicious server ACL events can be purged and blocked using the admin API.","published":"2023-10-10T17:17:11.146Z","modified":"2026-08-12T03:51:27.895818913Z","cvss":{"score":4.9,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.01166,"percentile":0.6573,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"matrix-synapse","fixedVersion":"1.94.0"}],"fix":{"url":"https://github.com/matrix-org/synapse/pull/16360","label":"matrix-org/synapse#16360"},"references":[{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/KEVRB4MG5UXQ5RLZHSUJXM5GWEBYYS5B/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/N6P4QULVUE254WI7XF2LWWOGHCYVFXFY/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WRO4MPQ6HOXIUZM6RJP6VTCTMV7RD2T3/"},{"type":"WEB","url":"https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#version-2-new-version"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/45xxx/CVE-2023-45129.json"},{"type":"ADVISORY","url":"https://github.com/matrix-org/synapse/security/advisories/GHSA-5chr-wjw5-3gq4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-45129"},{"type":"ADVISORY","url":"https://security.gentoo.org/glsa/202401-12"},{"type":"FIX","url":"https://github.com/matrix-org/synapse/pull/16360"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:27.895818913Z"}}