CVE-2021-22890

curl 7.63.0 to and including 7.75.0 includes vulnerability that allows a
malicious HTTPS proxy to MITM a connection due to bad handling of TLS 1.3
session tickets. When using a HTTPS proxy and TLS 1.3, libcurl can confuse
session tickets arriving from the HTTPS proxy but work as if they arrived
from the remote server and then wrongly “short-cut” the host handshake.
When confusing the tickets, a HTTPS proxy can trick libcurl to use the
wrong session ticket resume for the host and thereby circumvent the server
TLS certificate check and make a MITM attack to be possible to perform
unnoticed. Note that such a malicious HTTPS proxy needs to provide a
certificate that curl will accept for the MITMed server for an attack to
work - unless curl has been told to ignore the server certificate check.

Notes