Synapse CPU starvation (Denial of Service)
Priority LOW 29CWE-770Published · Updated
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-770.
Summary
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00128 2nd percentileScored 2026-11-07
Fix Fixed synapse (element-hq): 1.152.1matrix-synapse (PyPI): 1.152.1
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| element-hq | synapse | before 1.152.1 | 1.152.1 | Patch available | CNA |
| — | matrix-synapse (PyPI) | before 1.152.1 | 1.152.1 | Patch available | GHSA-8q93-326v-3m7g |
- synapse Vendorelement-hq Affected before 1.152.1 Fixed in 1.152.1 Patch available CNA
- matrix-synapse (PyPI) Vendor— Affected before 1.152.1 Fixed in 1.152.1 Patch available GHSA-8q93-326v-3m7g
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:element:synapse:*:*:*:*:*:*:*:* | before 1.152.1 | Vulnerable | element-hq |
- cpe:2.3:a:element:synapse:*:*:*:*:*:*:*:* Versions before 1.152.1 Vulnerable ·element-hq
Remediation
- Fix · CNA synapse (element-hq) Fixed in 1.152.1
- Fix · GHSA-8q93-326v-3m7g matrix-synapse (PyPI) Fixed in 1.152.1 Advisory →
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2026-45078
- 2026-10-03 Alias added: GHSA-8q93-326v-3m7g
References
Advisory 2
More element-hq Synapse vulnerabilities
- TI-2026-32924 Synapse pagination denial of service CVSS 4.0MEDIUM 5.1
Sources
- CVE-2026-45078 · CVE Program
- CVE-2026-45078 · NVD
- FIRST EPSS
- GHSA-8q93-326v-3m7g · GitHub Advisory Database · CC BY 4.0
- CVE-2026-45078 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences