CVE-2023-38686

What it is

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.

At a glance

Exploitability

Can be exploited from the same network segment without logging in. High risk of data exposure, data tampering.

Exploit odds

0.3% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2023-08-04 16:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 06:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.3% in the next 30 days (EPSS).
• Severity: 9.3 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2023-08-04 16:15 UTC

Last modified

2026-06-17 06:10 UTC

Exploit probability

0.3% · EPSS, next 30 days

Weakness

CWE-295 · Improper certificate validation

Record status

Modified

Affected

• Matrix Sydent < 2.5.6

Attack profile CVSS 3.1 · 9.3

Attack vector

Adjacent network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2023-38686.md and follow it. Check whether this project is affected by CVE-2023-38686. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge