CVE-2026-9547

A flaw was found in curl. When a libcurl-based application uses SCP:// or SFTP:// for transfers and employs the CURLOPT_SSH_KEYFUNCTION callback, it may silently accept an untrusted server. This occurs if the server's host key type differs from the one stored in the known_hosts file. The callback mechanism fails to enforce the host key restriction, enabling a connection to an untrusted server and risking a man-in-the-middle attack.

This is an Important flaw where libcurl-based applications performing SCP or SFTP transfers with the CURLOPT_SSH_KEYFUNCTION callback may silently accept an untrusted server. This occurs when a server presents a host key type that differs from the one recorded in the known_hosts file, bypassing a critical host key verification and enabling potential man-in-the-middle attacks. The vulnerability requires specific application callback usage, not a general curl client default.

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.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.