Vulnerability · Published May 28, 2026 · Assigned by GitHub_M

CVE-2026-45078Synapse CPU starvation (Denial of Service)

Medium 6.8

In plain English

A medium-severity resource allocation without limits in synapse from element-hq. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)6.8Medium

Exploit odds (30 days)0.1%top 97.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Alpine:v3.23	synapse	1.152.1-r0	ALPINE-CVE-2026-45078
Alpine:v3.24	synapse	1.152.1-r0	ALPINE-CVE-2026-45078
Debian:14	matrix-synapse	1.152.1-1	DEBIAN-CVE-2026-45078
PyPI	matrix-synapse	1.152.1	GHSA-8q93-326v-3m7g
PyPI	matrix-synapse	1.152.1	PYSEC-2026-191
Ubuntu:24.04:LTS	matrix-synapse	no fix listed	UBUNTU-CVE-2026-45078

Affected products (as reported)

Vendor	Product	Versions
element-hq	synapse	< 1.152.1

Weakness: CWE-770 · 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

References

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