CVE-2026-45078 PUBLISHED

Synapse CPU starvation (Denial of Service)

Assigner: GitHub_M
Reserved: 08.05.2026 Published: 28.05.2026 Updated: 28.05.2026

Synapse is an open source Matrix homeserver implementation. Prior to 1.152.1, local authenticated users can cause Synapse to starve other requests of CPU and lead to other requests failing, causing other users to be denied service. This vulnerability is fixed in 1.152.1.

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS Score: 6.8

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Local	Confidentiality	None	Confidentiality	None
Attack Complexity	Low	Integrity	None	Integrity	None
Attack Requirements	None	Availability	High	Availability	None
Privileges Required	Low
User Interaction	None

CVSS 4.0

Product Status

Vendor	element-hq
Product	synapse
Versions	Version < 1.152.1 is affected

References

https://github.com/element-hq/synapse/security/advisories/GHSA-8q93-326v-3m7g

Problem Types

CWE-770: Allocation of Resources Without Limits or Throttling CWE