CVE-2018-16515: PYSEC-2026-845 - Matrix Synapse Improper Signature Validation

CVE-2018-16515 · Severity: low · CVSS 3 · Published 2026-07-06

Matrix Synapse Improper Signature Validation

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

Quick answers

Is CVE-2018-16515 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2018-16515 being exploited in the wild.
How severe is CVE-2018-16515?
Low severity, with a CVSS score of 3, published 6 July 2026.
Which products and versions are affected?
matrix-synapse (PyPI) ECOSYSTEM:introduced=0,fixed=0.33.2.1,introduced=0.33.3,fixed=0.33.3.1, ECOSYSTEM:introduced=0.33.3,fixed=0.33.3.1.
Is there a fix for CVE-2018-16515?
Yes. matrix-synapse (PyPI): upgrade to 0.33.3.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2018-16515?
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 0.33.3.1 or later
    pip install "matrix-synapse>=0.33.3.1"

Affected products

  • matrix-synapse (PyPI) ECOSYSTEM:introduced=0,fixed=0.33.2.1,introduced=0.33.3,fixed=0.33.3.1, ECOSYSTEM:introduced=0.33.3,fixed=0.33.3.1

Identifiers

  • CVE-2018-16515
  • GHSA-fmvh-rvq5-hhjx
  • PYSEC-2026-845

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