{"cve":"CVE-2023-45129","nvd":{"published":"2023-10-10T18:15:19.093","modified":"2026-06-17T06:28:16.450","status":"Modified","description":"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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H","score":4.9},"cwes":["CWE-770"],"references":["https://github.com/matrix-org/synapse/pull/16360","https://github.com/matrix-org/synapse/security/advisories/GHSA-5chr-wjw5-3gq4","https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/KEVRB4MG5UXQ5RLZHSUJXM5GWEBYYS5B/","https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/N6P4QULVUE254WI7XF2LWWOGHCYVFXFY/","https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WRO4MPQ6HOXIUZM6RJP6VTCTMV7RD2T3/"],"products":["fedoraproject:fedora","matrix:synapse"],"source":"nvd","synced_at":"2026-10-19T21:39:34.467980132+00:00"},"epss":{"cve":"CVE-2023-45129","score":0.01394,"percentile":0.72385,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-5chr-wjw5-3gq4","url":"https://osv.dev/vulnerability/GHSA-5chr-wjw5-3gq4","summary":"matrix-synapse vulnerable to denial of service due to malicious server ACL events","modified":"2026-09-10T03:49:58.536596047Z","packages":[{"ecosystem":"PyPI","name":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","ranges":["<1.94.0"],"fixed":["1.94.0"]}]},{"id":"PYSEC-2023-199","url":"https://osv.dev/vulnerability/PYSEC-2023-199","summary":"","modified":"2023-11-08T04:13:36.773420Z","packages":[{"ecosystem":"PyPI","name":"matrix-synapse","purl":"pkg:pypi/matrix-synapse","ranges":["<1.94.0"],"fixed":["1.94.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}