9.3

CVE-2023-38686: matrix-org sydent Improper Certificate Validation

CVSS: 9.3v3.1CriticalModified
AliasesGHSA-p6hw-wm59-3g5gPYSEC-2023-139UBUNTU-CVE-2023-38686
Published 04-08-2023Last modified 08-10-2024
Open JSON

Vulnerability summary

CVE-2023-38686 is a critical (CVSS 9.3) Improper Certificate Validation vulnerability in matrix-org sydent. EPSS estimates a 0.27% chance of exploitation in the next 30 days, higher than 17.2% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.3/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.27%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 04-08-2023
    PublishedVulnerability first disclosed.
  2. 08-10-2024
    Last modifiedVulnerability information updated.

Description

Sydent is an identity server for the Matrix communications protocol. Prior to version 2.5.6, if configured to send emails using TLS, Sydent does not verify SMTP servers' certificates. This makes Sydent's emails vulnerable to interception via a man-in-the-middle (MITM) attack. Attackers with privileged access to the network can intercept room invitations and address confirmation emails. This is patched in Sydent 2.5.6. When patching, make sure that Sydent trusts the certificate of the server it is connecting to. This should happen automatically when using properly issued certificates. Those who use self-signed certificates should make sure to copy their Certification Authority certificate, or their self signed certificate if using only one, to the trust store of your operating system. As a workaround, one can ensure Sydent's emails fail to send by setting the configured SMTP server to a loopback or non-routable address under one's control which does not have a listening SMTP server.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.27%

Chance of exploitation in the next 30 days

Percentile

17%

Versus all other CVEs

30-day change

0.00 pp

From 0.27% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.27%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Matrix1 product
Matrix-org1 product
PyPI1 product
  • matrix-sydent< 1cd748307c6b168b66154e6c4db715d4b9551261 | < 2.5.6
Ubuntu1 product
  • matrix-sydentAll versions (No fix recorded)

4 vendors · 4 products

References

13 links
Show all 13 references