CVE-2026-55655 Details

A vulnerability exists in the OpenSSH client on Red Hat Enterprise Linux systems, allowing a local unprivileged attacker to hijack X11 forwarding connections. This is achieved by pre-binding the preferred abstract X socket name when X11 forwarding is enabled and a local UNIX-domain X socket is in use. The exploitation can compromise the confidentiality of the forwarded X11 traffic, including sensitive window contents and input, and may allow some manipulation of the forwarded session.

Users can disable X11 forwarding on OpenSSH clients when it is not needed by avoiding the use of '-X' or '-Y' options, or by setting 'ForwardX11 no' in the SSH client configuration file. On shared Linux systems with untrusted local users, it is advisable to avoid using client-side X11 forwarding until a fix is available.