Linux Distros Unpatched Vulnerability : CVE-2026-55655

medium Nessus Plugin ID 322158

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Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

- 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. (CVE-2026-55655)

Note that Nessus relies on the presence of the package as reported by the vendor.

Solution

There is no known solution at this time.

Plugin Details

Severity: Medium

ID: 322158

File Name: unpatched_CVE_2026_55655.nasl

Version: 1.9

Type: Local

Agent: unix

Family: Misc.

Published: 6/23/2026

Updated: 7/30/2026

Supported Sensors: Agentless Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Frictionless Assessment Azure, Nessus Agent, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.5

Percentile: 51.86

CVSS v2

Risk Factor: Low

Base Score: 3.3

Temporal Score: 2.8

Vector: CVSS2#AV:L/AC:M/Au:N/C:P/I:P/A:N

CVSS Score Source: CVE-2026-55655

CVSS v3

Risk Factor: Medium

Base Score: 6.1

Temporal Score: 5.6

Vector: CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N

Temporal Vector: CVSS:3.0/E:U/RL:U/RC:C

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:14.04:-:lts, cpe:/o:canonical:ubuntu_linux:16.04:-:lts, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, cpe:/o:canonical:ubuntu_linux:20.04:-:lts, cpe:/o:canonical:ubuntu_linux:22.04:-:lts, cpe:/o:canonical:ubuntu_linux:24.04:-:lts, cpe:/o:canonical:ubuntu_linux:25.10, cpe:/o:canonical:ubuntu_linux:26.04:-:lts, cpe:/o:centos:centos:7, cpe:/o:debian:debian_linux:11.0, cpe:/o:debian:debian_linux:12.0, cpe:/o:debian:debian_linux:13.0, cpe:/o:debian:debian_linux:14.0, cpe:/o:redhat:enterprise_linux:6, cpe:/o:redhat:enterprise_linux:7, p-cpe:/a:canonical:ubuntu_linux:openssh-ssh1, p-cpe:/a:canonical:ubuntu_linux:openssh, p-cpe:/a:centos:centos:openssh-askpass, p-cpe:/a:centos:centos:openssh-cavs, p-cpe:/a:centos:centos:openssh-clients, p-cpe:/a:centos:centos:openssh-keycat, p-cpe:/a:centos:centos:openssh-ldap, p-cpe:/a:centos:centos:openssh-server-sysvinit, p-cpe:/a:centos:centos:openssh-server, p-cpe:/a:centos:centos:openssh, p-cpe:/a:centos:centos:pam_ssh_agent_auth, p-cpe:/a:debian:debian_linux:openssh, p-cpe:/a:redhat:enterprise_linux:openssh-askpass, p-cpe:/a:redhat:enterprise_linux:openssh-cavs, p-cpe:/a:redhat:enterprise_linux:openssh-clients, p-cpe:/a:redhat:enterprise_linux:openssh-keycat, p-cpe:/a:redhat:enterprise_linux:openssh-ldap, p-cpe:/a:redhat:enterprise_linux:openssh-server-sysvinit, p-cpe:/a:redhat:enterprise_linux:openssh-server, p-cpe:/a:redhat:enterprise_linux:openssh, p-cpe:/a:redhat:enterprise_linux:pam_ssh_agent_auth

Required KB Items: Host/cpu, Host/local_checks_enabled, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 6/23/2026

Reference Information

CVE: CVE-2026-55655

Detections

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