CVE-2022-39374

Synapse Denial of service due to incorrect application of event authorization rules during state resolution

MEDIUM
6.5
CVSS Score
Published: May 26, 2023 at 01:44 PM UTC
Updated: June 17, 2026 at 04:58 AM UTC
2 products affected across 2 vendorsSynapseSynapse

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Severity
MEDIUM6.5
Exploit prediction
EPSS 0.9%
SSVC
No known exploit

Description

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. If Synapse and a malicious homeserver are both joined to the same room, the malicious homeserver can trick Synapse into accepting previously rejected events into its view of the current state of that room. This can be exploited in a way that causes all further messages and state changes sent in that room from the vulnerable homeserver to be rejected. This issue has been patched in version 1.68.0

Affected

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

1.62.0 ≤ v < 1.68.0
Affected range stops below 1.68.0, so it looks safe — our inference, not a vendor statement
v < 1.68.0
Affected range stops below 1.68.0, 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:

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

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

Quick Info

StatusMODIFIED
CWE
CWE-400

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