CVE-2025-30355

Name: CVE-2025-30355
Creator: NVD / NIST
Published: 2025-03-27T01:15:12.5+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.06%

Last modified Jun 17, 2026

CVE-2025-30355 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 1.06% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

1.06%

60.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-20

Affected Software

Vendor	Product	Versions
Matrix	Synapse	< 1.127.1

References

Timeline

Published: Mar 27, 2025
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2025-30355?

How severe is CVE-2025-30355?

CVE-2025-30355 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.06% probability of exploitation in the next 30 days.

How do I fix CVE-2025-30355?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-30355?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST