CVE-2023-40217

An issue was discovered in Python before 3.8.18, 3.9.x before 3.9.18,
3.10.x before 3.10.13, and 3.11.x before 3.11.5. It primarily affects
servers (such as HTTP servers) that use TLS client authentication. If a TLS
server-side socket is created, receives data into the socket buffer, and
then is closed quickly, there is a brief window where the SSLSocket
instance will detect the socket as “not connected” and won’t initiate a
handshake, but buffered data will still be readable from the socket buffer.
This data will not be authenticated if the server-side TLS peer is
expecting client certificate authentication, and is indistinguishable from
valid TLS stream data. Data is limited in size to the amount that will fit
in the buffer. (The TLS connection cannot directly be used for data
exfiltration because the vulnerable code path requires that the connection
be closed on initialization of the SSLSocket.)