CVE-2026-45076 | BDVDB-2026-336199 Detail

element-hqsynapse

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.

Impact#

Per CVSS v4.0: confidentiality impact none, integrity impact none, availability impact low. Attack vector: network.

Weaknesses#

CWE-20 Improper Input Validation

References#

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

Exploit#

No public exploit known

History#

Version 12026-05-28Record published in the CVE List.
Version 22026-06-02Most recent update recorded in the CVE List.

Published

Published: 2026-05-28
Last modified: 2026-06-02

Vendor information

Vendor: element-hq
Product: synapse

All element-hq vulnerabilities

Score

5.1 Medium

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 31.0.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Improper Input Validation

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
< 1.152.1
Fixed
Not stated

Scoring System

CVSS v4.0

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

Metric breakdown
Attack Vector	Network
Attack Complexity	Low
Attack Requirements	None
Privileges Required	High
User Interaction	None
Vulnerable System Confidentiality	None
Vulnerable System Integrity	None
Vulnerable System Availability	Low
Subsequent System Confidentiality	None
Subsequent System Integrity	None
Subsequent System Availability	None

CVSS v3.1

Not available

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).