TI-2024-20585 Aliases CVE-2024-31208 GHSA-3h7q-rfh9-xm4v

Synapse's V2 state resolution weakness allows DoS from remote room members

LOW 32CWE-770Published 2024-04-23 · Updated 2025-02-13

Key facts

Attack vector: Network
Privileges required: Low
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-770.

Summary

Synapse is an open-source Matrix homeserver. A remote Matrix user with malicious intent, sharing a room with Synapse instances before 1.105.1, can dispatch specially crafted events to exploit a weakness in the V2 state resolution algorithm. This can induce high CPU consumption and accumulate excessive data in the database of such instances, resulting in a denial of service. Servers in private federations, or those that do not federate, are not affected. Server administrators should upgrade to 1.105.1 or later. Some workarounds are available. One can ban the malicious users or ACL block servers from the rooms and/or leave the room and purge the room using the admin API.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.01463 73rd percentileScored 2026-11-07

Fix Fixed synapse (element-hq): 1.105.1matrix-synapse (PyPI): 1.105.1

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
element-hq	synapse	before 1.105.1	1.105.1	Patch available	CNA
—	matrix-synapse (PyPI)	before 1.105.1	1.105.1	Patch available	GHSA-3h7q-rfh9-xm4v

synapse Vendorelement-hq Affected before 1.105.1 Fixed in 1.105.1 Patch available CNA
matrix-synapse (PyPI) Vendor— Affected before 1.105.1 Fixed in 1.105.1 Patch available GHSA-3h7q-rfh9-xm4v

CPE configurations NVD · 4

CPE	Versions	Role	Vendor
cpe:2.3:a:matrix:synapse::::::::	before 1.105.1	Vulnerable	matrix-org
cpe:2.3:o:fedoraproject:fedora:38:::::::*	38	Vulnerable	Fedoraproject
cpe:2.3:o:fedoraproject:fedora:39:::::::*	39	Vulnerable	Fedoraproject
cpe:2.3:o:fedoraproject:fedora:40:::::::*	40	Vulnerable	Fedoraproject

cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:* Versions before 1.105.1 Vulnerable ·matrix-org
cpe:2.3:o:fedoraproject:fedora:38:*:*:*:*:*:*:* Versions 38 Vulnerable ·Fedoraproject
cpe:2.3:o:fedoraproject:fedora:39:*:*:*:*:*:*:* Versions 39 Vulnerable ·Fedoraproject
cpe:2.3:o:fedoraproject:fedora:40:*:*:*:*:*:*:* Versions 40 Vulnerable ·Fedoraproject

Remediation

Fix · CNA synapse (element-hq) Fixed in 1.105.1
Fix · GHSA-3h7q-rfh9-xm4v matrix-synapse (PyPI) Fixed in 1.105.1 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2024-31208
2026-10-03 Alias added: GHSA-3h7q-rfh9-xm4v

References

Patch 1

https://github.com/element-hq/synapse/commit/55b0aa847a61774b6a3acdc4b177a20dc019f01a

Advisory 5

Other 6

TI-2024-35327 Synapse allows a a malformed invite to break the invitee's `/sync` CVSS 4.0HIGH 8.7
TI-2024-36056 Synapse can be forced to thumbnail unexpected file formats, invoking external, potentially untrustworthy decoders CVSS 4.0HIGH 8.2
TI-2024-35318 Synapse allows unsupported content types to lead to memory exhaustion CVSS 4.0HIGH 8.2
TI-2022-07650 Remote program execution with user interaction CVSS 3.1HIGH 8.8
TI-2026-19372 ESS Community Helm Chart has a weak server key generation method CVSS 4.0CRITICAL 9.2
TI-2024-24814 Synapse denial of service through media disk space consumption CVSS 3.1HIGH 7.5

See all 31 →

Sources

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