Synapse Matrix has a partial room state leak via Sliding Sync

published 2024-12-03 23 mo ago modified 2026-07-07 4 mo ago also EUVD-2024-3430 , GHSA-56w4-5538-8v8h , PYSEC-2026-1610

cvss: 4.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits: 0; none known

Synapse is an open-source Matrix homeserver. The Sliding Sync feature on Synapse versions between 1.113.0rc1 and 1.120.0 can leak partial room state changes to users no longer in a room. Non-state events, like messages, are unaffected. This vulnerability is fixed in 1.120.1.

Patch / fix

fixed in 4 distros 2 links 1

pypi matrix-synapse 1.120.1
element-hq synapse 1.120.1
element synapse 1.120.1
matrix synapse 1.120.1

opensuse alpine

matrix-synapse openSUSE Tumbleweed 1.120.2-1.1

opensuse advisories openSUSE-SU-2024:14541-1

synapse Alpine 3.20 1.120.1
synapse Alpine 3.24, Alpine 3.23, Alpine 3.22 +1 more 1.120.2-r0

alpine advisories ALPINE-CVE-2024-53867

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

github.com/matrix-org/matrix-spec-proposals#4186 pull request

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2024-53867 updated 2025-11-21 cvss 3.7

matrix-synapse: Synapse Matrix has a partial room state leak via Sliding Sync

Red Hat All currently supported Red Hat products
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 23 mo ago (2024-12-03)

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
GitHub	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
OSV	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
pypi	matrix-synapse	>=1.113.0rc1, <1.120.1	1.120.1

Affected products

element-hq synapse

Classification

Weakness

CWE-497 Exposure of Sensitive System Information to an Unauthorized Control Sphere

References

github.com /matrix-org/matrix-spec-proposals/pull/4186
web
github.com /element-hq/synapse/security/advisories/GHSA-56w4-5538-8v8h
web
nvd.nist.gov /vuln/detail/CVE-2024-53867
advisory
github.com /element-hq/synapse
package
pypi.org /project/matrix-synapse
package
github.com /advisories/GHSA-56w4-5538-8v8h
advisory

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary