EUVD-2026-38413
GHSA-wcvf-3x75-j4c6
Severity by source
AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
Local-only attack requiring low-privilege account, race/pre-binding complexity, victim-initiated X11 session, and no availability impact independently support each metric choice.
Primary rating from Vendor (redhat).
CVSS VectorNVD
Lifecycle Timeline
2DescriptionNVD
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.
AnalysisAI
X11 forwarding session hijacking in OpenSSH enables a local unprivileged attacker sharing a Linux client host to intercept and partially manipulate the victim's forwarded X11 display traffic by squatting on the predictable abstract UNIX domain socket name before the SSH client creates it. Affected deployments span OpenSSH packages across Red Hat Enterprise Linux 6 through 10, Red Hat Hardened Images, and OpenShift Container Platform 4. No public exploit code has been identified at time of analysis, but successful exploitation yields high-confidence access to sensitive X11 session data including keystrokes, window contents, and clipboard material.
Technical ContextAI
OpenSSH's X11 forwarding feature tunnels X Window System display connections from a remote server back through the SSH encrypted channel to the client's local display. On Linux, the local endpoint for this forwarding is an abstract namespace UNIX domain socket - a Linux-specific socket variant identified by a null-byte prefix rather than a filesystem path, making it invisible to filesystem permissions and accessible to any process that knows or can guess the name. CWE-923 (Improper Restriction of Communication Channel to Intended Endpoints) identifies the root cause: the abstract socket name used for X11 forwarding is preferred or predictable, allowing an attacker to pre-bind it before the SSH client does. When the SSH client attempts to create the socket, it finds the name already taken and, depending on the implementation, may fall back to using the attacker's socket as the forwarding endpoint, directing the victim's X11 traffic through the attacker's process. CPE data confirms the affected products are OpenSSH as shipped in Red Hat Enterprise Linux (versions 6, 7, 8, 9, 10), Red Hat Hardened Images, and Red Hat OpenShift Container Platform 4.
RemediationAI
Consult the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-55655 for the patched OpenSSH package version, as no specific fixed version number has been confirmed in the available intelligence - patch availability per vendor advisory should be assumed pending confirmation. As the primary compensating control, disable X11 forwarding globally by setting 'ForwardX11 no' and 'ForwardX11Trusted no' in /etc/ssh/ssh_config on all client hosts; note this will block legitimate use of X11 application forwarding for users who depend on it. On systems where X11 forwarding is operationally required, restrict shell access to the client host to only trusted personnel to reduce local attacker surface. Migrating X application delivery to Wayland-native protocols eliminates this abstract socket attack surface entirely, though this requires compatible application and compositor support. Review /etc/ssh/ssh_config and per-user ~/.ssh/config files to audit where ForwardX11 or ForwardX11Trusted are enabled and restrict to sessions that genuinely require it.
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Same technique Information Disclosure
View allVendor StatusVendor
Debian
| Release | Status | Fixed Version | Urgency |
|---|---|---|---|
| bullseye | undetermined | 1:8.4p1-5+deb11u3 | - |
| bullseye (security) | undetermined | 1:8.4p1-5+deb11u7 | - |
| bookworm | undetermined | 1:9.2p1-2+deb12u10 | - |
| bookworm (security) | undetermined | 1:9.2p1-2+deb12u9 | - |
| trixie | undetermined | 1:10.0p1-7+deb13u4 | - |
| trixie (security) | undetermined | 1:10.0p1-7+deb13u2 | - |
| forky, sid | undetermined | 1:10.3p1-4 | - |
| (unstable) | fixed | undetermined | - |
SUSE
Severity: Moderate| Product | Status |
|---|---|
| SUSE Liberty Linux 10 | Fixed |
| SUSE Liberty Linux 8 | Fixed |
| SUSE Liberty Linux 9 | Fixed |
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