Home/CVE/Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. A malicious user on a S
CVE

CVE-2023-32323

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. A malicious user on a S

Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. A malicious user on a Synapse homeserver X with permission to create certain state events can disable outbound federation from X to an arbitrary homeserver Y. Synapse instances with federation disabled are not affected.

In versions of Synapse up to and including 1.73, Synapse did not limit the size of invite_room_state, meaning that it was possible to create an arbitrarily large invite event. Synapse 1.74 refuses to create oversized invite_room_state fields. Server operators should upgrade to Synapse 1.74 or newer urgently.

MEDIUM · CVSS 5 EPSS 0.00142
Schedule remediation
  • Public exploit or PoC is available
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-20Improper Input Validation
CWE-20Improper Input Validation
▤

Affected Products & Versions

1
matrix synapse< 1.74.0
▤

Affected Packages

1
Language-ecosystem packages (from OSV) tied to this CVE, with the version that fixes it - the dependency-level detail NVD doesn’t carry.
PyPI matrix-synapse MODERATE fixed in 1.74.0
⚠

Public Exploits & PoCs

1
pocgithub.com · 14492github.com
▣

Scoring & Timeline

5
MEDIUM · CVSS v3.1 · security-advisories@github.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD26 May 2023 · 02:15 PM
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L
SSVC triage · cisa-vulnrichment
Exploitation
poc
Automatable
no
Technical impact
partial
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
🔗

References & Sources

3
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/matrix-org/synapse/pull/14642Patch
https://github.com/matrix-org/synapse/security/advisories/GHSA-f3wc-3vxv-xmvrMitigationVendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UJIJRP5ZH6B3KGFLHCAKR2IX2Y4Z25QD/
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