Matrix Synapse before 0.33.3.1 allows remote attackers to spoof events and possibly have…
Priority MEDIUM 41CWE-347Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.0 · NVD. Fix status from CNA and GitHub. Impact type from CWE-347.
Summary
Matrix Synapse before 0.33.3.1 allows remote attackers to spoof events and possibly have unspecified other impacts by leveraging improper transaction and event signature validation.
Why it matters now
EPSS 0.01538 75th percentileScored 2026-11-07
Fix Fixed matrix-synapse (PyPI): 0.33.3.1, 0.33.2.1
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | — | all versions | — | No fix listed | CNA |
| — | matrix-synapse (PyPI) | 0.33.3 to before 0.33.3.1 | 0.33.3.1 | Patch available | GHSA-fmvh-rvq5-hhjx |
| — | matrix-synapse (PyPI) | before 0.33.2.1 | 0.33.2.1 | Patch available | GHSA-fmvh-rvq5-hhjx |
- — Vendor— Affected all versions Fixed in — No fix listed CNA
- matrix-synapse (PyPI) Vendor— Affected 0.33.3 to before 0.33.3.1 Fixed in 0.33.3.1 Patch available GHSA-fmvh-rvq5-hhjx
- matrix-synapse (PyPI) Vendor— Affected before 0.33.2.1 Fixed in 0.33.2.1 Patch available GHSA-fmvh-rvq5-hhjx
CPE configurations NVD · 2
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:* | before 0.33.3.1 | Vulnerable | matrix-org |
| cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:* | 8.0 | Vulnerable | Debian |
- cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:* Versions before 0.33.3.1 Vulnerable ·matrix-org
- cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:* Versions 8.0 Vulnerable ·Debian
Remediation
- Fix · GHSA-fmvh-rvq5-hhjx matrix-synapse (PyPI) Fixed in 0.33.3.1 Advisory →
- Fix · GHSA-fmvh-rvq5-hhjx matrix-synapse (PyPI) Fixed in 0.33.2.1 Advisory →
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2018-16515
- 2026-10-03 Alias added: GHSA-fmvh-rvq5-hhjx
References
Advisory 3
Other 7
- https://github.com/matrix-org/synapse/commit/5bf8bc79ebc22c61968f2eb487714813fccbdb9b
- https://github.com/matrix-org/synapse/commit/804dd41e18c449e711e443398b95c9f6c68b6fa2
- https://github.com/matrix-org/synapse/commit/a5a0bf5cf71caed3c4e3677d2bce667c147dadfc
- https://github.com/matrix-org/synapse/commit/c127c8d0421f0228a46ebbe280c9537e8d8ea42b
- https://github.com/matrix-org/synapse
- https://lists.fedoraproject.org/archives/list/[email protected]/message/IRW7YR2H3ASUSYX4AO4KMY3FNVDNYW3P
- https://matrix.org/blog/2018/09/06/critical-security-update-synapse-0-33-3-1
Sources
- CVE-2018-16515 · CVE Program
- CVE-2018-16515 · NVD
- FIRST EPSS
- GHSA-fmvh-rvq5-hhjx · GitHub Advisory Database · CC BY 4.0
- CVE-2018-16515 · 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