GHSA-p6hw-wm59-3g5g · Severity: critical · Ecosystem: pip — Sydent does not verify email server certificates
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.
Conclusion & alert: CVE-2023-38686 is rated Moderate Risk (42.1/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.23%). Mandatory action: Review affected assets and schedule remediation.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-06-15 | 0.06% | 0.23% | +0.17% |
| 2 | 2023-08-11 | 0.04% | 0.06% | +0.02% |
| 3 | 2023-08-05 | — | 0.04% | — |
Full EPSS history (3 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 9.3 | 3.1 | CRITICAL |
|
2.8 | 5.8 | [email protected] |
| 5.3 | 3.1 | MEDIUM |
|
1.6 | 3.6 | [email protected] |
GHSA-p6hw-wm59-3g5g · Severity: critical · Ecosystem: pip — Sydent does not verify email server certificates
| vendor | priority | summary | link |
|---|---|---|---|
ubuntu
|
medium | CVE-2023-38686 medium priority: Ubuntu including 1 source packages (matrix-sydent), 12 status rows across 12 suites (bionic, focal, jammy, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): ignored 6, DNE 3, needs-triage 2, needed 1. | https://ubuntu.com/security/CVE-2023-38686 |
| URL | Tags |
|---|---|
| https://docs.python.org/3/library/ssl.html?highlight=ssl#security-considerations | Technical Description |
| https://github.com/matrix-org/sydent/commit/1cd748307c6b168b66154e6c4db715d4b9551261 | Patch |
| https://github.com/matrix-org/sydent/pull/574 | Issue Tracking Patch |
| https://github.com/matrix-org/sydent/releases/tag/v2.5.6 | Release Notes |
| https://github.com/matrix-org/sydent/security/advisories/GHSA-p6hw-wm59-3g5g | Vendor Advisory |
| https://github.com/python/cpython/issues/91826 | Issue Tracking |
| https://peps.python.org/pep-0476/ | Third Party Advisory |