CVE-2025-30355: PYSEC-2026-1614 - Synapse vulnerable to federation denial of service via malformed events

CVE-2025-30355 · Severity: low · CVSS 3.1 · Published 2026-07-07

Synapse vulnerable to federation denial of service via malformed events

Technologies: matrix-synapse (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2025-30355 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2025-30355 being exploited in the wild.
How severe is CVE-2025-30355?
Low severity, with a CVSS score of 3.1, published 7 July 2026.
Which products and versions are affected?
matrix-synapse (PyPI) ECOSYSTEM:introduced=0,fixed=1.127.1.
Is there a fix for CVE-2025-30355?
Yes. matrix-synapse (PyPI): upgrade to 1.127.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2025-30355?
Check whether you run matrix-synapse (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • matrix-synapse (PyPI): upgrade to 1.127.1 or later
    pip install "matrix-synapse>=1.127.1"

Affected products

  • matrix-synapse (PyPI) ECOSYSTEM:introduced=0,fixed=1.127.1

Identifiers

  • CVE-2025-30355
  • GHSA-v56r-hwv5-mxg6
  • PYSEC-2026-1614

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