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certfr-2026-avi-1243 — De multiples vulnérabilités ont été découvertes dans CPython. Elles permettent à un attaquant de provoquer un déni de s…

2026-10-03T00:43:48.615672+00:00

certfr-2026-avi-1243

fkie_cve-2026-19553

2026-10-03T00:43:48.615769+00:00

This defect could lead to programs where certificate hostname verification *appeared* to be succeeding with SSLContext.check_hostname = True and no ValueError being raised due to misconfiguration.

If the program passes a server_hostname value that isn't an empty string or None to any of these APIs then certificate hostname verification proceeds as expected and the program is not affected by this vulnerability.

Mitigating this vulnerability doesn't require updating Python or applying the patch. To mitigate, pass a valid non-None and non-empty server_hostname value to SSLContext.wrap_bio(), asyncio.create_connection(), or asyncio.loop.start_tls() and certificate hostname verification will proceed as expected. Upgrading to the latest version of Python or applying the patch only changes the behavior from silently skipping hostname verification to raising a ValueError, similar to SSLContext.wrap_socket(), when server_hostname isn't supplied.

GHSA-xx9w-qm94-hghj

2026-10-03T00:43:48.615840+00:00

This defect could lead to programs where certificate hostname verification *appeared* to be succeeding with SSLContext.check_hostname = True and no ValueError being raised due to misconfiguration.

RHSA-2026:74587 — Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

2026-10-03T00:43:48.615875+00:00

python: python: Certificate verification bypass via missing server_hostname validation in SSLContext.wrap_bio()

UBUNTU-CVE-2026-19553

2026-10-03T00:43:48.615901+00:00

Affected: Ubuntu:Pro:14.04:LTS: python2.7, Ubuntu:Pro:14.04:LTS: python3.4, Ubuntu:Pro:14.04:LTS: python3.5, Ubuntu:Pro:16.04:LTS: python2.7, Ubuntu:Pro:16.04:LTS: python3.5, Ubuntu:Pro:18.04:LTS: python2.7, Ubuntu:Pro:18.04:LTS: python3.6, Ubuntu:Pro:18.04:LTS: python3.7, Ubuntu:Pro:18.04:LTS: python3.8, Ubuntu:Pro:20.04:LTS: python3.8 and 7 more

ssl.SSLContext.wrap_bio() didn't require the server_hostname argument to not be None if ssl.SSLContext.check_hostname was set. Due to a missing parameter check in SSLObject, if the server_hostname argument isn't supplied then hostname verification would be silently skipped. This defect could lead to programs where certificate hostname verification *appeared* to be succeeding with SSLContext.check_hostname = True and no ValueError being raised due to misconfiguration. If the program passes a server_hostname value that isn't an empty string or None to any of these APIs then certificate hostname verification proceeds as expected and the program is not affected by this vulnerability. Mitigating this vulnerability doesn't require updating Python or applying the patch. To mitigate, pass a valid non-None and non-empty server_hostname value to SSLContext.wrap_bio(), asyncio.create_connection(), or asyncio.loop.start_tls() and certificate hostname verification will proceed as expected. Upgrading to the latest version of Python or applying the patch only changes the behavior from silently skipping hostname verification to raising a ValueError, similar to SSLContext.wrap_socket(), when server_hostname isn't supplied.