CVE-2024-31208

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

MEDIUM
6.5
CVSS Score
Published: April 23, 2024 at 05:26 PM UTC
Updated: June 17, 2026 at 07:27 AM UTC
3 products affected across 3 vendorsFedoraSynapseSynapse

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Severity
MEDIUM6.5
Exploit prediction
EPSS 1%
SSVC
No known exploit

Description

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.

Affected

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

v < 1.105.1
Affected range stops below 1.105.1, so it looks safe — our inference, not a vendor statement
v < 1.105.1
Affected range stops below 1.105.1, 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

6.5MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-770

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