Improper input validation in Element-hq Synapse
CVE-2025-30355
Synapse is an open source Matrix homeserver implementation. A malicious server can craft events which, when received, prevent Synapse version up to 1.127.0 from federating with other servers. The vulnerability has been exploited in the wil…
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
EPSS: 0.132 (94.3th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H.
Affected products
- Element-hq Synapse — versions < 1.127.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- https://github.com/element-hq/synapse/security/advisories/GHSA-v56r-hwv5-mxg6 (x_refsource_CONFIRM)
- https://github.com/element-hq/synapse/commit/2277df2a1eb685f85040ef98fa21d41aa4cdd389 (x_refsource_MISC)
- https://github.com/element-hq/synapse/releases/tag/v1.127.1 (x_refsource_MISC)
Frequently asked questions
- What is CVE-2025-30355?
- CVE-2025-30355 is a high-severity vulnerability in Element-hq Synapse, classified under Improper Input Validation. CVSS score: 7.1/10. Published 2025-03-27.
- How severe is CVE-2025-30355?
- High severity. CVSS v3 base score is 7.1 out of 10.
- Is CVE-2025-30355 known to be exploited?
- 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.