There is a MEDIUM severity vulnerability affecting CPython.

The
 “socket” module provides a pure-Python fallback to the 
socket.socketpair() function for platforms that don’t support AF_UNIX, 
such as Windows. This pure-Python implementation uses AF_INET or 
AF_INET6 to create a local connected pair of sockets. The connection 
between the two sockets was not verified before passing the two sockets 
back to the user, which leaves the server socket vulnerable to a 
connection race from a malicious local peer.

Platforms that support AF_UNIX such as Linux and macOS are not affected by this vulnerability. Versions prior to CPython 3.5 are not affected due to the vulnerable API not being included.

The
 “socket” module provides a pure-Python fallback to the 
socket.socketpair() function for platforms that don’t support AF_UNIX, 
such as Windows. This pure-Python implementation uses AF_INET or 
AF_INET6 to create a local connected pair of sockets. The connection 
between the two sockets was not verified before passing the two sockets 
back to the user, which leaves the server socket vulnerable to a 
connection race from a malicious local peer.

Platforms that support AF_UNIX such as Linux and macOS are not affected by this vulnerability. Versions prior to CPython 3.5 are not affected due to the vulnerable API not being included.

Python Software Foundation CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Python Software Foundation AV:L/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X