CVE-2024-5642

CPython 3.9 and earlier doesn’t disallow configuring an empty list (“[]”)
for SSLContext.set_npn_protocols() which is an invalid value for the
underlying OpenSSL API. This results in a buffer over-read when NPN is used
(see CVE-2024-5535 for OpenSSL). This vulnerability is of low severity due
to NPN being not widely used and specifying an empty list likely being
uncommon in-practice (typically a protocol name would be configured).

Notes