CVE-2023-45129

matrix-synapse vulnerable to denial of service due to malicious server ACL events

Published Oct 10, 2023 CVSS 3.1 · 4.9 Medium EPSS 1.4% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2023-0135 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.
Github GHSA Github GHSA GHSA-5chr-wjw5-3gq4 matrix-synapse vulnerable to denial of service due to malicious server ACL events
Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Feb 13, 2025, 5:13 PM
Reserved
Oct 4, 2023, 4:02 PM
Status
Modified
Published
Oct 10, 2023, 6:15 PM
Modified
Jun 17, 2026, 6:28 AM
Severity
Moderate
Public date
Oct 10, 2023, 12:00 AM