Linux Distros Unpatched Vulnerability : CVE-2026-55653

medium Nessus Plugin ID 322159

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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 malicious SSH server can exploit a double free vulnerability in the Diffie- Hellman Group Exchange (DH-GEX) client path. This occurs during FIPS (Federal Information Processing Standards) mode known-group validation when the client processes attacker-controlled DH-GEX group parameters. Successful exploitation leads to client-side process termination, resulting in a Denial of Service (DoS). (CVE-2026-55653)

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: 322159

File Name: unpatched_CVE_2026_55653.nasl

Version: 1.7

Type: Local

Agent: unix

Family: Misc.

Published: 6/23/2026

Updated: 7/2/2026

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

Risk Information

VPR

Risk Factor: Low

Score: 3

Percentile: 23.71

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 7

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

CVSS Score Source: CVE-2026-55653

CVSS v3

Risk Factor: Medium

Base Score: 6.5

Temporal Score: 6.2

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

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

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:20.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:openssh, p-cpe:/a:redhat:enterprise_linux:openssh-cavs, cpe:/o:canonical:ubuntu_linux:24.04:-:lts, cpe:/o:redhat:enterprise_linux:6, p-cpe:/a:centos:centos:openssh-ldap, p-cpe:/a:centos:centos:openssh-server, cpe:/o:canonical:ubuntu_linux:25.10, p-cpe:/a:centos:centos:openssh-clients, p-cpe:/a:centos:centos:openssh-server-sysvinit, cpe:/o:redhat:enterprise_linux:9, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, p-cpe:/a:redhat:enterprise_linux:openssh, cpe:/o:centos:centos:8, p-cpe:/a:centos:centos:openssh-keysign, p-cpe:/a:redhat:enterprise_linux:openssh-keycat, p-cpe:/a:redhat:enterprise_linux:pam_ssh_agent_auth, p-cpe:/a:canonical:ubuntu_linux:openssh-ssh1, cpe:/o:redhat:enterprise_linux:8, cpe:/o:redhat:enterprise_linux:10, p-cpe:/a:redhat:enterprise_linux:openssh-server-sysvinit, cpe:/o:canonical:ubuntu_linux:14.04:-:lts, p-cpe:/a:redhat:enterprise_linux:openssh-keysign, p-cpe:/a:redhat:enterprise_linux:openssh-askpass, p-cpe:/a:centos:centos:openssh-keycat, p-cpe:/a:centos:centos:openssh, p-cpe:/a:centos:centos:openssh-askpass, cpe:/o:canonical:ubuntu_linux:26.04:-:lts, p-cpe:/a:redhat:enterprise_linux:openssh-clients, cpe:/o:centos:centos:7, cpe:/o:canonical:ubuntu_linux:16.04:-:lts, cpe:/o:redhat:enterprise_linux:7, p-cpe:/a:redhat:enterprise_linux:openssh-server, p-cpe:/a:redhat:enterprise_linux:openssh-ldap, p-cpe:/a:centos:centos:pam_ssh_agent_auth, cpe:/o:canonical:ubuntu_linux:22.04:-:lts, p-cpe:/a:centos:centos:openssh-cavs

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

Exploit Available: true

Exploit Ease: Exploits are available

Vulnerability Publication Date: 6/23/2026

Reference Information

CVE: CVE-2026-55653

Detections

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