OpenSSH X11 Forwarding Hijack via local X Socket Pre-binding
CVE-2026-55655 Published on June 23, 2026
Openssh: local mitm of x11 forwarding via abstract unix socket pre-binding in red hat enterprise linux openssh client versions
A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side X11 forwarding connections. This is possible by pre-binding the preferred abstract X socket name when X11 forwarding is enabled and a local UNIX-domain X socket is used. A successful attack can compromise the confidentiality of forwarded X11 traffic, including sensitive window contents and input, and may allow some manipulation of the forwarded session.
Vulnerability Analysis
CVE-2026-55655 can be exploited with local system access, requires user interaction and a small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality, with no impact on integrity, and no impact on availability.
Timeline
Reported to Red Hat.
Made public. 57 days later.
Weakness Type
Improper Restriction of Communication Channel to Intended Endpoints
The software establishes a communication channel to (or from) an endpoint for privileged or protected operations, but it does not properly ensure that it is communicating with the correct endpoint.
Products Associated with CVE-2026-55655
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