CVE-2026-45076

Synapse pagination denial of service

State: Published
Severity: 5.1 Medium
Published: May 28, 2026
Updated: Jun 2, 2026
Reserved: May 8, 2026

Description

Synapse is an open source Matrix homeserver implementation. Prior to 1.152.1, in federated rooms, malicious homeservers can craft room events in such a way that prevents Synapse from providing full history to paginating clients. Clients could therefore fail to display room history. This vulnerability is fixed in 1.152.1.

Scores

CVSS	Score	Vector	Source
4.0	5.1 Medium	CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N	GitHub_M

Weaknesses

CWE-20 Improper Input Validation

Affected Products

Product	Versions
synapseelement-hq	< 1.152.1Affected

References

https://github.com/element-hq/synapse/security/advisories/GHSA-6qf2-7x63-mm6v

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