Enterprise LinuxOperating system · Redhat
CVE-2026-55655
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceOpenSSH contains a local privilege escalation vulnerability in its X11 forwarding implementation on Linux clients. An unprivileged local attacker can pre-bind the abstract X socket name used by OpenSSH for X11 forwarding, allowing them to hijack the forwarded X11 connection and intercept sensitive window contents, input data, and potentially manipulate the session.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Enterprise LinuxOperating system
= 6.0= 7.0= 8.0= 9.0= 10.0all versionsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Identify OpenSSH versionRun 'ssh -V' or 'rpm -q openssh' on RHEL systems to determine installed OpenSSH versionAffected if Installed version matches Redhat Enterprise Linux 6.0, 7.0, 8.0, 9.0, 10.0 or is an OpenBSD version of OpenSSH
-
Verify X11 forwarding is enabled in SSH client configurationInspect /etc/ssh/ssh_config and ~/.ssh/config for 'X11Forwarding yes' directiveAffected if X11Forwarding is set to yes or is uncommented (default enabled)
-
Check for active X11 forwarding sessionRun 'echo $DISPLAY' to see if an X display is set, or use 'ss -x | grep -E ":[0-9]+.*ssh"' to look for active X11 forwarded socketsAffected if DISPLAY variable is set to an abstract socket (format typically :10, :11 etc) or active SSH X11 forwarding sockets exist
-
Inspect SSH client configuration for X11 forwarding optionsReview /etc/ssh/ssh_config for 'ForwardX11' and 'ForwardX11Trusted' settingsAffected if ForwardX11 is enabled (yes or trusted mode)
The environment is affected if OpenSSH version matches the affected RHEL versions or is OpenBSD-based AND X11 forwarding is enabled in SSH client configuration and actively in use.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataDisable X11 forwarding on OpenSSH clients unless explicitly required, or use alternative display mechanisms like Xpra/SSH -X with additional access controls. Apply vendor patches when available. Consider restricting local X socket access via filesystem permissions.
Fix this in Enterprise Linux
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-55655 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-55655 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data