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CVE-2026-19553 on Cyberus Linux 26.05

Aliases: CVE-2026-19553

Packages: python311, python312, python313, python314, python315

Status: Plausible

Advisory Information

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.

Updates

2026-10-01 01:39 CEST

Metadata changes:

  • Status for package python311: “Plausible”
  • Status for package python312: “Plausible”
  • Status for package python313: “Plausible”
  • Status for package python314: “Plausible”
  • Status for package python315: “Plausible”

2026-10-01 01:39 CEST

Metadata changes:

  • Status for package python311: “New”
  • Status for package python312: “New”
  • Status for package python313: “New”
  • Status for package python314: “New”
  • Status for package python315: “New”