CVE-2026-5545

CVE-2026-5545 · wrong reuse of HTTP Negotiate connection

This page contains facts from public vulnerability sources. Check the original advisory before updating.

This page shows selected source facts. See the linked advisories for the complete description and affected versions.

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...

CVSS 6.5 · Medium · EPSS 0.4% · Fix available

Published

2026-05-13T08:27:26.065Z

Updated

2026-09-15T06:02:59.285Z

Stack: system

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