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CVE-2018-16515

27
FAUCET Score

CVE-2018-16515 describes a critical vulnerability in Matrix Synapse versions prior to 0.33.3.1, affecting Debian Linux distributions. This flaw allows remote attackers to spoof events due to improper transaction and event signature validation. With a CVSS score of 8.8 (High), this vulnerability presents a significant risk, enabling high impact to confidentiality, integrity, and availability with low attack complexity and requiring only low privileges. Despite its severity, there is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.33.3.1CPE matchmatch criteria
cpe:2.3:a:matrix:synapse:*:*:*:*:*:*:*:*
8.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

8.8HIGH

CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.52%
Probability of exploitation in next 30 days
EPSS Percentile
72.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.0152 is in the 70th percentile among its peer group of 17,822 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

github_advisorypatch availablevia nvd_reference
View patch
pippatch availablevia ghsa
Product: matrix-synapseFixed in: 0.33.3.1
pippatch availablevia ghsa
Product: matrix-synapseFixed in: 0.33.2.1

Vendor Advisories (1)

pipGHSA-fmvh-rvq5-hhjxhigh

Matrix Synapse Improper Signature Validation

May 13, 2022

References

github.com / matrix-org/synapse/issues/3796
PatchThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/IRW7YR2H3ASUSYX4AO4KMY3FNVDNYW3P
matrix.org / blog/2018/09/06/critical-security-update-synapse-0-33-3-1
Vendor Advisory