CPython 3.9 and earlier doesn't disallow configuring an empty list ("[]") for SSLContext.setnpnprotocols() 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).
{
"cpes": [
"cpe:2.3:a:python:python:*:*:*:*:*:*:*:*"
],
"severity": "Medium"
}