CVE-2026-5545

libcurl might in some circumstances reuse the wrong connection when asked to

do an authenticated HTTP(S) request after a Negotiate-authenticated one, when

both use the same host.

libcurl features a pool of recent connections so that subsequent requests can

reuse an existing connection to avoid overhead.

When reusing a connection a range of criteria must be met. Due to a logical

error in the code, a request that was issued by an application could

wrongfully reuse an existing connection to the same server that was

authenticated using different credentials.

An application that first uses Negotiate authentication to a server with

`user1:password1` and then does another operation to the same server asking

for any authentication method but for `user2:password2` (while the previous

connection is still alive) - the second request gets confused and wrongly

reuses the same connection and sends the new request over that connection

thinking it uses a mix of user1's and user2's credentials when it is in fact

still using the connection authenticated for user1...