Room Event Manipulation in Synapse by Element HQ
CVE-2026-45076

5.1MEDIUM

Key Information:

Vendor

Element-hq

Status
Synapse
Vendor
CVE Published:
28 May 2026

What is CVE-2026-45076?

Synapse, an open-source Matrix homeserver implementation by Element HQ, has a vulnerability affecting federated rooms. Malicious homeservers can craft specific room events that prevent Synapse from delivering complete room history to clients. As a result, users may experience incomplete or missing room history during pagination. This issue has been addressed in version 1.152.1 of Synapse.

Affected Version(s)

synapse < 1.152.1

References

https://github.com/element-hq/synapse/security/advisories...
x_refsource_CONFIRM

CVSS V4

Score:
5.1
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.