Amazon Linux 2023 : openssh, openssh-clients, openssh-keycat (ALAS2023-2026-1745)

medium Nessus Plugin ID 316944

Synopsis

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

Description

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-1745 advisory.

Vulnerability in the OpenSSH GSSAPI delta included in various Linux distributions. This vulnerability affects the GSSAPI patches added by various Linux distributions and does not affect the OpenSSH upstream project itself. The usage of sshpkt_disconnect() on an error, which does not terminate the process, allows an attacker to send an unexpected GSSAPI message type during the GSSAPI key exchange to the server, which will call the underlying function and continue the execution of the program without setting the related connection variables. As the variables are not initialized to NULL the code later accesses those uninitialized variables, accessing random memory, which could lead to undefined behavior. The recommended workaround is to use ssh_packet_disconnect() instead, which does terminate the process. The impact of the vulnerability depends heavily on the compiler flag hardening configuration. (CVE-2026-3497)

In OpenSSH before 10.3, command execution can occur via shell metacharacters in a username within a command line. This requires a scenario where the username on the command line is untrusted, and also requires a non-default configurations of % in ssh_config. (CVE-2026-35386)

OpenSSH before 10.3 can use unintended ECDSA algorithms. Listing of any ECDSA algorithm in PubkeyAcceptedAlgorithms or HostbasedAcceptedAlgorithms is misinterpreted to mean all ECDSA algorithms.
(CVE-2026-35387)

OpenSSH before 10.3 omits connection multiplexing confirmation for proxy-mode multiplexing sessions.
(CVE-2026-35388)

OpenSSH before 10.3 mishandles the authorized_keys principals option in uncommon scenarios involving a principals list in conjunction with a Certificate Authority that makes certain use of comma characters.
(CVE-2026-35414)

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 2023.11.20260526' or or 'dnf update --advisory ALAS2023-2026-1745 --releasever 2023.11.20260526' to update your system.

Plugin Details

Severity: Medium

ID: 316944

File Name: al2023_ALAS2023-2026-1745.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 5/27/2026

Updated: 5/27/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

CVSS v2

Risk Factor: High

Base Score: 7.6

Temporal Score: 5.6

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

CVSS Score Source: CVE-2026-35414

CVSS v3

Risk Factor: High

Base Score: 8.1

Temporal Score: 7.1

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

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

CVSS v4

Risk Factor: Medium

Base Score: 6.9

Threat Score: 2.7

Threat Vector: CVSS:4.0/E:U

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

CVSS Score Source: CVE-2026-3497

Vulnerability Information

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

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

Exploit Ease: No known exploits are available

Patch Publication Date: 5/26/2026

Vulnerability Publication Date: 3/12/2026

Reference Information

CVE: CVE-2026-3497, CVE-2026-35386, CVE-2026-35387, CVE-2026-35388, CVE-2026-35414

IAVA: 2026-A-0296

Detections

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