CVE-2023-38686 Sydent does not verify email server certificates

2023-08-0415:57:15

CWE-295

GitHub_M

www.cve.org

sydent

email server

certificate

vulnerability

patched

version 2.5.6

interception

man-in-the-middle attack

network access

room invitations

address confirmation

tls

smtp server

trust store

operating system

self-signed certificate

workaround

9.3 High

CVSS3

Attack Vector

ADJACENT

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

HIGH

Integrity Impact

HIGH

Availability Impact

NONE

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

9.2 High

AI Score

Confidence

High

0.001 Low

EPSS

Percentile

26.6%

JSON

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.

CNA Affected

[
  {
    "vendor": "matrix-org",
    "product": "sydent",
    "versions": [
      {
        "version": "< 2.5.6",
        "status": "affected"
      }
    ]
  }
]