What is the CVSS score of CVE-2025-30355?

CVE-2025-30355 has a CVSS 3.1 base score of 7.1 (High). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H. EPSS exploitation probability: 7.5%.

Which versions of Synapse are affected by CVE-2025-30355?

Organizations using Synapse face moderate risk from CVE-2025-30355, a input validation vulnerability rated CVSS 7.1. Exploitation could compromise the security of affected deployments.. A patch is available.

How to fix or mitigate CVE-2025-30355?

Within 7 days: Identify all affected systems and apply vendor patches promptly. Vendor patch is available.

Synapse CVE-2025-30355

HIGH

Improper Input Validation (CWE-20)

2025-03-27 security-advisories@github.com

Information Disclosure Synapse Suse

7.1

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

7.1 HIGH

AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H

SUSE

HIGH

qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 28, 2026 - 18:33 vuln.today

Patch released

Mar 28, 2026 - 18:33 nvd

Patch available

CVE Published

Mar 27, 2025 - 01:15 nvd

HIGH 7.1

DescriptionGitHub Advisory

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 wild and has been fixed in Synapse v1.127.1. No known workarounds are available.

AnalysisAI

Synapse is an open source Matrix homeserver implementation. Rated high severity (CVSS 7.1), this vulnerability is remotely exploitable, low attack complexity.

Technical ContextAI

This vulnerability is classified under CWE-20. 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 wild and has been fixed in Synapse v1.127.1. No known workarounds are available. Affected products include: Matrix Synapse. Version information: up to 1.127.0.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.