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CVE-2026-19553

SSLContext.wrap_bio() missing validation of server_hostname parameter PUBLISHED

Description (CNA)

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.

Affected (CNA)

Vendor / productVersions
Python Software Foundation / CPythonaffected 0 before 3.10.22; affected 3.11.0 before 3.11.17; affected 3.12.0 before 3.12.15; affected 3.13.0 before 3.13.16; affected 3.14.0 before 3.14.8; affected 3.15.0a1 before 3.15.0rc3

CWE

CWE-297

References

ADP enrichment

CVE

No English description supplied.

CISA-ADP

No English description supplied.

No references supplied.