Amazon Linux 2023 : openssh, openssh-clients, openssh-keycat (ALAS2023-2026-2031)

critical Nessus Plugin ID 332008

Synopsis

The remote Amazon Linux 2023 host is missing a security update.

Description

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2031 advisory.

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)

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)

scp in OpenSSH before 10.4 may place a file in the parent directory of an intended directory when the copy occurs between two remote destinations. (CVE-2026-59996)

ssh in OpenSSH before 10.4 can have a use-after-free when a server changes its host key during a key re- exchange. (This outcome occurs only on the client side.) (CVE-2026-60002)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Run 'dnf update openssh --releasever 2023.12.20260803' or or 'dnf update --advisory ALAS2023-2026-2031 --releasever 2023.12.20260803' to update your system.

Plugin Details

Severity: Critical

ID: 332008

File Name: al2023_ALAS2023-2026-2031.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 8/4/2026

Updated: 8/4/2026

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

Risk Information

VPR

Risk Factor: Medium

Score: 4.5

Percentile: 57.61

CVSS v2

Risk Factor: High

Base Score: 9.7

Temporal Score: 7.6

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

CVSS Score Source: CVE-2026-60002

CVSS v3

Risk Factor: Critical

Base Score: 9.4

Temporal Score: 8.4

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

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

Vulnerability Information

CPE: cpe:/o:amazon:linux:2023, p-cpe:/a:amazon:linux:openssh-clients-debuginfo, p-cpe:/a:amazon:linux:openssh-clients, p-cpe:/a:amazon:linux:openssh-debuginfo, p-cpe:/a:amazon:linux:openssh-debugsource, p-cpe:/a:amazon:linux:openssh-keycat-debuginfo, p-cpe:/a:amazon:linux:openssh-keycat, p-cpe:/a:amazon:linux:openssh-server-debuginfo, p-cpe:/a:amazon:linux:openssh-server, p-cpe:/a:amazon:linux:openssh-sk-dummy-debuginfo, p-cpe:/a:amazon:linux:openssh-sk-dummy, p-cpe:/a:amazon:linux:openssh, p-cpe:/a:amazon:linux:pam_ssh_agent_auth-debuginfo, p-cpe:/a:amazon:linux:pam_ssh_agent_auth

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 8/4/2026

Vulnerability Publication Date: 6/23/2026

Reference Information

CVE: CVE-2026-55653, CVE-2026-55655, CVE-2026-59996, CVE-2026-60002

IAVA: 2026-A-0691

Detections

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