CVE-2023-38686

Advisory

Matrix-sydent 2.5.6 includes a fix for an Improper Certificate Validation vulnerability.
https://github.com/matrix-org/sydent/pull/574
https://github.com/matrix-org/sydent/security/advisories/GHSA-p6hw-wm59-3g5g

Affected package

Affected versions

Fixed versions

Vulnerability changelog

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. See CVE-2023-38686.


MISC:https://docs.python.org/3/library/ssl.html?highlight=ssl#security-considerations: https://docs.python.org/3/library/ssl.html?highlight=ssl#security-considerations
MISC:https://github.com/matrix-org/sydent/commit/1cd748307c6b168b66154e6c4db715d4b9551261: https://github.com/matrix-org/sydent/commit/1cd748307c6b168b66154e6c4db715d4b9551261
MISC:https://github.com/matrix-org/sydent/pull/574: https://github.com/matrix-org/sydent/pull/574
MISC:https://github.com/matrix-org/sydent/releases/tag/v2.5.6: https://github.com/matrix-org/sydent/releases/tag/v2.5.6
MISC:https://github.com/matrix-org/sydent/security/advisories/GHSA-p6hw-wm59-3g5g: https://github.com/matrix-org/sydent/security/advisories/GHSA-p6hw-wm59-3g5g
MISC:https://github.com/python/cpython/issues/91826: https://github.com/python/cpython/issues/91826
MISC:https://peps.python.org/pep-0476/: https://peps.python.org/pep-0476/

Resources

• https://docs.python.org/3/library/ssl.html?highlight=ssl#security-considerations
• https://github.com/matrix-org/sydent/commit/1cd748307c6b168b66154e6c4db715d4b9551261
• https://github.com/matrix-org/sydent/pull/574
• https://github.com/matrix-org/sydent/releases/tag/v2.5.6
• https://github.com/matrix-org/sydent/security/advisories/GHSA-p6hw-wm59-3g5g
• https://github.com/python/cpython/issues/91826
• https://peps.python.org/pep-0476/
• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-38686