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VulnerabilityPublished Updated

CVE-2026-55655: Openssh ssh1 · A flaw was found in OpenSSH

Affects openssh-ssh1Source GCVE Database

0
Authoritative record:CVE-2026-55655· Medium 5.0

Not known to be exploited · CVSS 5.0 Medium.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score
5.0Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.09% chance of exploitation in 30 days – higher than 0% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 23 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu 26.10openssh-ssh1pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=stonkingOther threatsAffected
  • =1:7.5p1-18
  • =1:7.5p1-18ubuntu1
  • =1:7.5p1-18ubuntu2
Fixed in–
Ubuntu 26.04 LTSopenssh-ssh1pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=resoluteOther threatsAffected
  • =1:7.5p1-17
  • =1:7.5p1-18
Fixed in–
Ubuntu 25.10opensshpkg:deb/ubuntu/openssh?arch=source&distro=questingOther threatsAffected
  • 1:9.9p1-3ubuntu3 – 1:10.0p1-5ubuntu5.4
8 affected builds
Fixed in–
Ubuntu 25.10openssh-ssh1pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=questingOther threatsAffected
  • =1:7.5p1-17
Fixed in–
Ubuntu 24.04 LTSopenssh-ssh1pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=nobleOther threatsAffected
  • 1:7.5p1-14 – 1:7.5p1-16
4 affected builds
Fixed in–
Ubuntu 22.04 LTSopenssh-ssh1pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=jammyOther threatsAffected
  • =1:7.5p1-12
  • =1:7.5p1-12build1
  • =1:7.5p1-13
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

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.

References

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