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

Source: https://junglewise.ai/threats/cve-2023-38686-sydent-does-not-verify-email-server-certificates  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2023-08-04  
License: CC BY 4.0 with a link back

CVE-2023-38686 · Severity: low · CVSS 3.1 · Published 2023-08-04

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.

Technologies: [matrix-sydent (PyPI)](https://junglewise.ai/threats/technologies/matrix-sydent). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2023-38686 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2023-38686 being exploited in the wild.

**How severe is CVE-2023-38686?** Low severity, with a CVSS score of 3.1, published 4 August 2023.

**Which products and versions are affected?** matrix-sydent (PyPI) ECOSYSTEM:introduced=0,fixed=2.5.6, GIT:introduced=0,fixed=1cd748307c6b168b66154e6c4db715d4b9551261|ECOSYSTEM:introduced=0,fixed=2.5.6.

**Is there a fix for CVE-2023-38686?** Yes. matrix-sydent (PyPI): upgrade to 2.5.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2023-38686?** Check whether you run matrix-sydent (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- matrix-sydent (PyPI): upgrade to 2.5.6 or later

  ```sh
  pip install "matrix-sydent>=2.5.6"
  ```


## Affected products

- matrix-sydent (PyPI) ECOSYSTEM:introduced=0,fixed=2.5.6, GIT:introduced=0,fixed=1cd748307c6b168b66154e6c4db715d4b9551261|ECOSYSTEM:introduced=0,fixed=2.5.6

## Identifiers

- CVE-2023-38686
- GHSA-p6hw-wm59-3g5g
- PYSEC-2023-139

## Related threats

- [PYSEC-2026-2620 - matrix-sydent and matrix-synapse Use Cryptographically Weak PRNG](https://junglewise.ai/threats/cve-2019-11842-matrix-sydent-and-matrix-synapse-use-cryptographically-weak-prng)
- [PYSEC-2026-843 - Matrix Sydent mishandles emails](https://junglewise.ai/threats/cve-2019-11340-matrix-sydent-mishandles-emails)
- [SSRF in Sydent due to missing validation of hostnames](https://junglewise.ai/threats/cve-2021-29431-ssrf-in-sydent-due-to-missing-validation-of-hostnames)
- [Malicious users could abuse Sydent to control the content of invitation emails](https://junglewise.ai/threats/cve-2021-29432-malicious-users-could-abuse-sydent-to-control-the-content-of)
- [Sydent vulnerable to denial of service attack via memory exhaustion](https://junglewise.ai/threats/cve-2021-29430-sydent-vulnerable-to-denial-of-service-attack-via-memory)