CVE-2026-5545

A flaw was found in libcurl. An application using libcurl that performs an authenticated HTTP(S) request after a Negotiate-authenticated one to the same host may incorrectly reuse the previous connection. This authentication bypass vulnerability allows the second request to be sent over a connection authenticated with different credentials, potentially leading to unauthorized access or information disclosure.

Moderate: A flaw in libcurl allows for the wrong reuse of HTTP Negotiate authenticated connections. This can occur when an application makes an authenticated HTTP(S) request after a Negotiate-authenticated one to the same host, potentially leading to a request being sent over a connection authenticated with unintended credentials. This issue affects applications using libcurl versions from 7.10.6 up to and including 8.19.0.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, applications using libcurl can disable connection reuse. This can be achieved by setting one of the following libcurl options: CURLOPT_FRESH_CONNECT to force a new connection for each request, CURLOPT_MAXCONNECTS to limit the total number of open connections, or CURLMOPT_MAX_HOST_CONNECTIONS when using the curl_multi API to limit connections per host. Disabling connection reuse may impact application performance due to increased overhead for establishing new connections.