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Fencer Vulns
high 8.8

CVE-2018-16515 json

Matrix Synapse Improper Signature Validation

published 2018-09-18 8 y ago modified 2026-07-07 4 mo ago also GHSA-fmvh-rvq5-hhjx , PYSEC-2026-845 , EUVD-2022-3811

cvss
8.8
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 75%
public exploits
0
none known

Summary

Matrix Synapse before 0.33.3.1 allows remote attackers to spoof events and possibly have unspecified other impacts by leveraging improper transaction and event signature validation.

Patch / fix

  • pypi matrix-synapse 0.33.2.1, 0.33.3.1
  • matrix synapse 0.33.3.1
  • matrix-synapse Ubuntu Pro 18.04 LTS 0.24.0+dfsg-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2018-16515

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-16515 updated

matrix-synapse: pre-disclosure of critical vulnerability

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.54% chance of exploitation in the next 30 days, higher than 75% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 8.8 CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.5 AV:N/AC:L/Au:S/C:P/I:P/A:P
OSV 3.0 8.8 CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
GitHub 3.0 8.8 CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
pypi matrix-synapse
>=0.33.3, <0.33.3.1
<0.33.2.1
0.33.3.1
0.33.2.1

Classification

Weakness
  • CWE-347 Improper Verification of Cryptographic Signature

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.