CVE-2026-45078

Synapse CPU starvation (Denial of Service)

Published May 28, 2026 CVSS 4.0 · 6.8 Medium EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-8q93-326v-3m7g Synapse CPU starvation (Denial of Service)
History
Type Values Removed Values Added
First Time appeared Element
Element synapse
CPEs cpe:2.3:a:element:synapse:*:*:*:*:*:*:*:*
Vendors & Products Element
Element synapse
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Element-hq
Element-hq synapse
Vendors & Products Element-hq
Element-hq synapse
Type Values Removed Values Added
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.
Title Synapse CPU starvation (Denial of Service)
Weaknesses CWE-770
References
Metrics cvssV4_0

{'score': 6.8, '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
May 29, 2026, 3:31 PM
Reserved
May 8, 2026, 6:45 PM
Status
Analyzed
Published
May 28, 2026, 5:16 PM
Modified
Oct 26, 2026, 1:10 PM