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Openssh ssh1: A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side X11 forwarding connections. (CVE-2026-55655)

0
Medium
VulnerabilityCVE-2026-55655gcveosvubuntu-cve-2026-55655ubuntu-pro-14-04-ltsubuntu-pro-16-04-ltsubuntu-pro-fips-16-04-ltsubuntu-pro-18-04-ltsubuntu-18-04-ltsubuntu-pro-fips-updates-18-04-ubuntu-pro-fips-18-04-ltsubuntu-pro-20-04-ltsubuntu-20-04-ltsubuntu-pro-fips-updates-20-04-ubuntu-pro-fips-20-04-ltsubuntu-22-04-ltsubuntu-pro-fips-preview-22-04-ubuntu-pro-fips-updates-22-04-ubuntu-24-04-ltsubuntu-pro-fips-updates-24-04-ubuntu-25-10ubuntu-26-04-ltscve-2026-55655cwe-923ghsa-wcvf-3x75-j4c6ghsa
Published: 06/23/2026 (06/23/2026, 04:17:00 UTC)
Source: GCVE Database
Product: openssh-ssh1

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.

CVSS v3.1

Score 6.1medium

Attack Vector
Local
Attack Complexity
Low
Privileges Required
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

Affected software

Ubuntu:Pro:14.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:6.6p1-2ubuntu2.13+esm2?arch=source&distro=esm-infra-legacy/trusty
Affected versions
=1:6.2p2-6=1:6.2p2-6ubuntu1=1:6.4p1-1=1:6.4p1-2=1:6.5p1-1=1:6.5p1-2=1:6.5p1-3=1:6.5p1-4=1:6.5p1-6=1:6.6p1-1=1:6.6p1-2=1:6.6p1-2ubuntu1=1:6.6p1-2ubuntu2=1:6.6p1-2ubuntu2.2=1:6.6p1-2ubuntu2.3=1:6.6p1-2ubuntu2.4=1:6.6p1-2ubuntu2.6=1:6.6p1-2ubuntu2.7=1:6.6p1-2ubuntu2.8=1:6.6p1-2ubuntu2.10=1:6.6p1-2ubuntu2.11=1:6.6p1-2ubuntu2.12=1:6.6p1-2ubuntu2.13=1:6.6p1-2ubuntu2.13+esm1=1:6.6p1-2ubuntu2.13+esm2
Ubuntu:Pro:16.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.2p2-4ubuntu2.10+esm8?arch=source&distro=esm-infra-legacy/xenial
Affected versions
=1:6.9p1-2=1:6.9p1-3=1:7.1p1-1=1:7.1p1-3=1:7.1p1-4=1:7.1p1-6=1:7.1p2-1=1:7.1p2-2=1:7.2p1-1=1:7.2p2-1=1:7.2p2-2=1:7.2p2-3=1:7.2p2-4=1:7.2p2-4ubuntu1=1:7.2p2-4ubuntu2.1=1:7.2p2-4ubuntu2.2=1:7.2p2-4ubuntu2.4=1:7.2p2-4ubuntu2.5=1:7.2p2-4ubuntu2.6=1:7.2p2-4ubuntu2.7=1:7.2p2-4ubuntu2.8=1:7.2p2-4ubuntu2.10=1:7.2p2-4ubuntu2.10+esm1=1:7.2p2-4ubuntu2.10+esm2=1:7.2p2-4ubuntu2.10+esm3=1:7.2p2-4ubuntu2.10+esm4=1:7.2p2-4ubuntu2.10+esm5=1:7.2p2-4ubuntu2.10+esm6=1:7.2p2-4ubuntu2.10+esm7=1:7.2p2-4ubuntu2.10+esm8
Ubuntu:Pro:FIPS:16.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.2p2-4ubuntu2.fips.2.10.1?arch=source&distro=fips/xenial
Affected versions
=1:7.2p2-4ubuntu2.fips.2.2=1:7.2p2-4ubuntu2.fips.2.2.1=1:7.2p2-4ubuntu2.fips.2.10.1
Ubuntu:Pro:18.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.6p1-4ubuntu0.7+esm4?arch=source&distro=esm-infra/bionic
Affected versions
=1:7.5p1-10=1:7.6p1-4=1:7.6p1-4ubuntu0.1=1:7.6p1-4ubuntu0.2=1:7.6p1-4ubuntu0.3=1:7.6p1-4ubuntu0.5=1:7.6p1-4ubuntu0.6=1:7.6p1-4ubuntu0.7=1:7.6p1-4ubuntu0.7+esm1=1:7.6p1-4ubuntu0.7+esm2=1:7.6p1-4ubuntu0.7+esm3=1:7.6p1-4ubuntu0.7+esm4
Ubuntu:18.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=bionic
Affected versions
=1:7.5p1-8=1:7.5p1-9=1:7.5p1-9build1=1:7.5p1-10
Ubuntu:Pro:FIPS-updates:18.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.9p1-10~ubuntu18.04.fips.0.10?arch=source&distro=fips-updates/bionic
Affected versions
=1:7.9p1-10~ubuntu18.04.fips.0.1=1:7.9p1-10~ubuntu18.04.fips.0.2=1:7.9p1-10~ubuntu18.04.fips.0.3=1:7.9p1-10~ubuntu18.04.fips.0.4=1:7.9p1-10~ubuntu18.04.fips.0.5=1:7.9p1-10~ubuntu18.04.fips.0.6=1:7.9p1-10~ubuntu18.04.fips.0.7=1:7.9p1-10~ubuntu18.04.fips.0.8=1:7.9p1-10~ubuntu18.04.fips.0.9=1:7.9p1-10~ubuntu18.04.fips.0.10
Ubuntu:Pro:FIPS:18.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:7.9p1-10~ubuntu18.04.fips.0.2?arch=source&distro=fips/bionic
Affected versions
=1:7.9p1-10~ubuntu18.04.fips.0.1=1:7.9p1-10~ubuntu18.04.fips.0.2
Ubuntu:Pro:20.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.2p1-4ubuntu0.13+esm1?arch=source&distro=esm-infra/focal
Affected versions
=1:8.0p1-6build1=1:8.1p1-1=1:8.1p1-5=1:8.2p1-4=1:8.2p1-4ubuntu0.1=1:8.2p1-4ubuntu0.2=1:8.2p1-4ubuntu0.3=1:8.2p1-4ubuntu0.4=1:8.2p1-4ubuntu0.5=1:8.2p1-4ubuntu0.7=1:8.2p1-4ubuntu0.8=1:8.2p1-4ubuntu0.9=1:8.2p1-4ubuntu0.10=1:8.2p1-4ubuntu0.11=1:8.2p1-4ubuntu0.12=1:8.2p1-4ubuntu0.13=1:8.2p1-4ubuntu0.13+esm1
Ubuntu:20.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=focal
Affected versions
=1:7.5p1-11build1
Ubuntu:Pro:FIPS-updates:20.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.2p1-4ubuntu0.fips.0.13.1?arch=source&distro=fips-updates/focal
Affected versions
=1:8.2p1-4ubuntu0.fips.0.2.1=1:8.2p1-4ubuntu0.fips.0.4.0=1:8.2p1-4ubuntu0.fips.0.5.0=1:8.2p1-4ubuntu0.fips.0.7=1:8.2p1-4ubuntu0.fips.0.8=1:8.2p1-4ubuntu0.fips.0.9=1:8.2p1-4ubuntu0.fips.0.10=1:8.2p1-4ubuntu0.fips.0.11=1:8.2p1-4ubuntu0.fips.0.12=1:8.2p1-4ubuntu0.fips.0.13=1:8.2p1-4ubuntu0.fips.0.13.1
Ubuntu:Pro:FIPS:20.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.2p1-4ubuntu0.fips.0.2.1?arch=source&distro=fips/focal
Affected versions
=1:8.2p1-4ubuntu0.fips.0.2.1
Ubuntu:22.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.9p1-3ubuntu0.16?arch=source&distro=jammy
Affected versions
=1:8.4p1-6ubuntu2=1:8.7p1-2=1:8.7p1-2build1=1:8.7p1-4=1:8.8p1-1=1:8.9p1-3=1:8.9p1-3ubuntu0.1=1:8.9p1-3ubuntu0.3=1:8.9p1-3ubuntu0.4=1:8.9p1-3ubuntu0.5=1:8.9p1-3ubuntu0.6=1:8.9p1-3ubuntu0.7=1:8.9p1-3ubuntu0.10=1:8.9p1-3ubuntu0.11=1:8.9p1-3ubuntu0.13=1:8.9p1-3ubuntu0.14=1:8.9p1-3ubuntu0.15=1:8.9p1-3ubuntu0.16
Ubuntu:22.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=jammy
Affected versions
=1:7.5p1-12=1:7.5p1-12build1=1:7.5p1-13
Ubuntu:Pro:FIPS-preview:22.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.9p1-3ubuntu1.fips.0~ppa3?arch=source&distro=fips-preview/jammy
Affected versions
=1:8.9p1-3ubuntu0.4+Fips1=1:8.9p1-3ubuntu0.4+Fips3=1:8.9p1-3ubuntu1.fips.0~ppa3
Ubuntu:Pro:FIPS-updates:22.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:8.9p1-3ubuntu1.fips.0~ppa3?arch=source&distro=fips-updates/jammy
Affected versions
=1:8.9p1-3ubuntu0.4+Fips1=1:8.9p1-3ubuntu0.4+Fips3=1:8.9p1-3ubuntu0.6+Fips1=1:8.9p1-3ubuntu0.7+Fips1=1:8.9p1-3ubuntu0.10+Fips1=1:8.9p1-3ubuntu0.11+Fips1=1:8.9p1-3ubuntu0.13+Fips1=1:8.9p1-3ubuntu0.14+Fips1=1:8.9p1-3ubuntu0.15+Fips1=1:8.9p1-3ubuntu0.15+Fips3=1:8.9p1-3ubuntu1.fips.0~ppa3
Ubuntu:24.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:9.6p1-3ubuntu13.18?arch=source&distro=noble
Affected versions
=1:9.3p1-1ubuntu3=1:9.4p1-1ubuntu1=1:9.6p1-3ubuntu1=1:9.6p1-3ubuntu2=1:9.6p1-3ubuntu11=1:9.6p1-3ubuntu12=1:9.6p1-3ubuntu13=1:9.6p1-3ubuntu13.3=1:9.6p1-3ubuntu13.4=1:9.6p1-3ubuntu13.5=1:9.6p1-3ubuntu13.7=1:9.6p1-3ubuntu13.8=1:9.6p1-3ubuntu13.9=1:9.6p1-3ubuntu13.11=1:9.6p1-3ubuntu13.12=1:9.6p1-3ubuntu13.13=1:9.6p1-3ubuntu13.14=1:9.6p1-3ubuntu13.15=1:9.6p1-3ubuntu13.16=1:9.6p1-3ubuntu13.18
Ubuntu:24.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=noble
Affected versions
=1:7.5p1-14=1:7.5p1-15=1:7.5p1-15build1=1:7.5p1-16
Ubuntu:Pro:FIPS-updates:24.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:9.6p1-3ubuntu13.16+Fips2?arch=source&distro=fips-updates/noble
Affected versions
=1:9.6p1-3ubuntu13.7+Fips1=1:9.6p1-3ubuntu13.12+Fips1=1:9.6p1-3ubuntu13.13+Fips1=1:9.6p1-3ubuntu13.14+Fips1=1:9.6p1-3ubuntu13.15+Fips1=1:9.6p1-3ubuntu13.16+Fips1=1:9.6p1-3ubuntu13.16+Fips2
Ubuntu:25.10more threats →ghsa
openssh
pkg:deb/ubuntu/openssh?arch=source&distro=questing
Affected versions
=1:9.9p1-3ubuntu3=1:9.9p1-3ubuntu3.1=1:10.0p1-5ubuntu2=1:10.0p1-5ubuntu3=1:10.0p1-5ubuntu4=1:10.0p1-5ubuntu5=1:10.0p1-5ubuntu5.1=1:10.0p1-5ubuntu5.4
Ubuntu:25.10more threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=questing
Affected versions
=1:7.5p1-17
Ubuntu:26.04:LTSmore threats →ghsa
openssh
pkg:deb/ubuntu/openssh@1:10.2p1-2ubuntu3.5?arch=source&distro=resolute
Affected versions
=1:10.0p1-5ubuntu5=1:10.2p1-2ubuntu1=1:10.2p1-2ubuntu3=1:10.2p1-2ubuntu3.2=1:10.2p1-2ubuntu3.4=1:10.2p1-2ubuntu3.5
Ubuntu:26.04:LTSmore threats →ghsa
openssh-ssh1
pkg:deb/ubuntu/openssh-ssh1?arch=source&distro=resolute
Affected versions
=1:7.5p1-17=1:7.5p1-18

Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.

Technical Details

Gcve Source
db.gcve.eu
Osv Id
UBUNTU-CVE-2026-55655
Osv Schema Version
1.7.0
Ecosystems
["Ubuntu:Pro:14.04:LTS","Ubuntu:Pro:16.04:LTS","Ubuntu:Pro:FIPS:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:18.04:LTS","Ubuntu:Pro:FIPS-updates:18.04:LTS","Ubuntu:Pro:FIPS:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:20.04:LTS","Ubuntu:Pro:FIPS-updates:20.04:LTS","Ubuntu:Pro:FIPS:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:Pro:FIPS-preview:22.04:LTS","Ubuntu:Pro:FIPS-updates:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:Pro:FIPS-updates:24.04:LTS","Ubuntu:25.10","Ubuntu:26.04:LTS"]
Cvss Version
3.1
State
PUBLISHED

Threat ID: 6a5e7a702a4a8d59899de932

Added to database: 07/20/2026, 19:43:44 UTC

Last updated: 09/13/2026, 13:03:35 UTC

Views: 162

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