CVE-2026-55655: A flaw was found in OpenSSH

Routine

MEDIUM 5.0WATCHLISTMITIGATEMITIGATE

CVE-2026-55655 is a medium-severity flaw (CVSS 5.0) affecting openssh, enterprise linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 forwarde

Why this priority

On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.0 (Medium)
Attack vector	Local
Attack complexity	High
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.1% (top 99%)
CISA exploited list	No
Weakness	CWE-923
Published	2026-06-23
Last modified	2026-10-26

Publisher (CNA): Red Hat, Inc. · Vendor: openbsd · redhat

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-23 04:17 UTCPublished CVE record published
2026-10-26 04:17 UTCUpdated Record last modified

openbsd openssh MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy openssh || rpm -q openssh || openssh --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

redhat enterprise linux MITIGATE

Affected: 6.0 · 7.0 · 8.0 · 9.0 · 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-55655?

openssh: mitigate or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-55655 being exploited?

CVE-2026-55655 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-55655 affect?

CVE-2026-55655 affects openssh, enterprise linux. Severity is medium (CVSS 5.0). 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 l

How urgent is CVE-2026-55655?

Priority 23/100. On your watchlist

Software pages

OpenSSH vulnerabilities

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References

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