CVE-2024-5642: Python Software Foundation Cpython

Medium severity, CVSS 6.5. EPSS: 0.7% chance of exploitation in the next 30 days.

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).

Affected products

• Python Software Foundation Cpython: before 3.9.24 (fixed in 3.9.24); from 3.10.0a1, before 3.10.0b1 (fixed in 3.10.0b1)

Published 2024-06-27. Last modified 2026-07-31.