CVE-2023-45129

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

MEDIUM
4.9
CVSS Score
Published: October 10, 2023 at 05:17 PM UTC
Updated: June 17, 2026 at 06:28 AM UTC
3 products affected across 3 vendorsFedoraSynapseSynapse

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Severity
MEDIUM4.9
Exploit prediction
EPSS 1%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 1.94.0
Affected range stops below 1.94.0, so it looks safe — our inference, not a vendor statement
v < 1.94.0
Affected range stops below 1.94.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

CVSS

4.9MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
HIGH
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-770

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