Python.org contains an exploitable denial-of-service vulnerability in its X509 certificate parser. A specially crafted X509 certificate can cause a NULL pointer dereference, resulting in a denial of service. Python can crash if getpeercert() is called on a TLS connection, which uses a certificate with invalid DistributionPoint in its extension.

https://blog.talosintelligence.com/2019/01/vulnerability-spotlight-pythonorg.html