HOMEVULNERABILITIESCVE-2023-45129
MEDIUM

CVE-2023-45129

CWE-770Published: October 10, 2023· Updated: Jun 17, 2026

4.9
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2023-45129 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires high privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 4.9.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.High
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H

Affected Vendors & Products

Fedora1 product(s)
fedora
matrix1 product(s)
synapse
Source: NVD CPE · 3 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/matrix-org/synapse/pull/16360
PATCHhttps://github.com/matrix-org/synapse/pull/16360
ADVISORYhttps://github.com/matrix-org/synapse/security/advisories/GHSA-5chr-wjw5-3gq4
ADVISORYhttps://github.com/matrix-org/synapse/security/advisories/GHSA-5chr-wjw5-3gq4

All References (14)

→
https://github.com/matrix-org/synapse/pull/16360Patch · Vendor Advisory
→
https://github.com/matrix-org/synapse/security/advisories/GHSA-5chr-wjw5-3gq4Vendor Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/KEVRB4MG5UXQ5RLZHSUJXM5GWEBYYS5B/Mailing List
→
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/Mailing List
→
https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#version-2-new-versionRelease Notes
→
https://security.gentoo.org/glsa/202401-12
→
https://github.com/matrix-org/synapse/pull/16360Patch · Vendor Advisory
→
https://github.com/matrix-org/synapse/security/advisories/GHSA-5chr-wjw5-3gq4Vendor Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/KEVRB4MG5UXQ5RLZHSUJXM5GWEBYYS5B/Mailing List
→
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/Mailing List
→
https://matrix-org.github.io/synapse/latest/admin_api/rooms.html#version-2-new-versionRelease Notes
→
https://security.gentoo.org/glsa/202401-12

Quick Facts

CVE IDCVE-2023-45129
CVSS Score4.9 / 10
SeverityMEDIUM
WeaknessCWE-770
CISA KEVNo
Affected2 vendor(s)
PublishedOct 10, 2023

Related CVEs (CWE-770)

CVE-2022-3456
9.8
CVE-2022-3273
9.8
CVE-2022-3439
9.8
CVE-2023-25156
9.8
CVE-2018-20033
9.8
CVE-2025-11832
9.8

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2023-45129 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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