Amazon Linux 2023 : libssh, libssh-config, libssh-devel (ALAS2023-2026-3096)

high Nessus Plugin ID 351083

Synopsis

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

Description

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-3096 advisory.

A flaw was found in libssh. A remote authenticated client can issue SSH_FXP_READ requests with an arbitrarily large length, causing a libssh SFTP server to allocate excessive memory and potentially exhaust it through repeated requests. (CVE-2026-59844)

A flaw was found in libssh. When ProxyCommand is used, an unchecked fork() failure can be stored as process ID -1; during cleanup, signals may then be sent across the caller's accessible process tree, leading to local denial of service. (CVE-2026-59845)

A flaw was found in libssh. A malicious username expanded through %r in ProxyCommand handling can inject shell metacharacters, exposing environment variables and causing unintended shell behavior.
(CVE-2026-59846)

A flaw was found in libssh. Incorrect AES-GCM finalization checks in builds using the OpenSSL backend can effectively remove integrity protection, allowing an in-path attacker to modify plaintext on the wire without detection. (CVE-2026-59847)

A flaw was found in libssh. A malicious SFTP server can send responses for unknown request IDs that libssh clients keep queued indefinitely, causing unbounded memory growth and client-side denial of service.
(CVE-2026-59848)

A flaw was found in libssh. If data packets are processed after a channel is closed, channel data callbacks can be invoked after the associated data has already been freed, leading to crashes or possible use-after-free conditions. (CVE-2026-59850)

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 libssh --releasever 2023.12.20260928' or or 'dnf update --advisory ALAS2023-2026-3096 --releasever 2023.12.20260928' to update your system.

Plugin Details

Severity: High

ID: 351083

File Name: al2023_ALAS2023-2026-3096.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 9/29/2026

Updated: 9/29/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.3

Percentile: 51.06

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

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

CVSS Score Source: CVE-2026-59847

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

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

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

Vulnerability Information

CPE: cpe:/o:amazon:linux:2023, p-cpe:/a:amazon:linux:libssh-config, p-cpe:/a:amazon:linux:libssh-debuginfo, p-cpe:/a:amazon:linux:libssh-debugsource, p-cpe:/a:amazon:linux:libssh-devel, p-cpe:/a:amazon:linux:libssh

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

Exploit Ease: No known exploits are available

Patch Publication Date: 9/29/2026

Vulnerability Publication Date: 7/21/2026

Reference Information

CVE: CVE-2026-59844, CVE-2026-59845, CVE-2026-59846, CVE-2026-59847, CVE-2026-59848, CVE-2026-59850

IAVA: 2026-A-0788

Detections

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