Detections
Analytics

Ubuntu 22.04 LTS / 24.04 LTS / 26.04 LTS : libssh vulnerabilities (USN-8699-1)

high Nessus Plugin ID 365394

Synopsis

The remote Ubuntu host is missing one or more security updates.

Description

The remote Ubuntu 22.04 LTS / 24.04 LTS / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8699-1 advisory.

 It was discovered that libssh had a stack buffer overflow in its SFTP server when constructing directory listing entries for long filenames. An attacker could possibly use this issue to cause libssh to crash or execute arbitrary code. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-15370)

 It was discovered that libssh did not correctly handle SSH channel open messages advertising a zero maximum packet size. An authenticated remote attacker could possibly use this issue to cause libssh to consume excessive CPU resources, leading to a denial of service. (CVE-2026-59843)

 It was discovered that libssh did not correctly limit SFTP read request lengths in its server implementation. An authenticated remote attacker could possibly use this issue to cause libssh to allocate excessive memory, leading to a denial of service. This issue only affected Ubuntu 26.04 LTS.
 (CVE-2026-59844)

 It was discovered that libssh did not correctly handle ProxyCommand fork() failures. A local attacker could possibly use this issue to cause a denial of service. (CVE-2026-59845)

 It was discovered that libssh did not correctly sanitize shell metacharacters when expanding usernames in ProxyCommand strings. An attacker could possibly use this issue to obtain sensitive information.
 (CVE-2026-59846)

 It was discovered that libssh had incorrect AES-GCM tag verification when built with the OpenSSL backend.
 A machine-in-the-middle attacker could possibly use this issue to modify encrypted traffic without detection. (CVE-2026-59847)

 It was discovered that libssh did not correctly handle SFTP server responses for unknown request IDs. An attacker could possibly use this issue to cause libssh to use excessive memory, leading to a denial of service. (CVE-2026-59848)

 It was discovered that libssh had logic errors in certificate-based authentication that could cause clients to loop indefinitely when certificates were rejected. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-59849)

 It was discovered that libssh could invoke data callbacks on channels after they had been closed. An attacker could possibly use this issue to cause libssh to crash or execute arbitrary code.
 (CVE-2026-59850)

Tenable has extracted the preceding description block directly from the Ubuntu 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

Update the affected libssh-4 and / or libssh-gcrypt-4 packages.

See Also

https://ubuntu.com/security/notices/USN-8699-1

Plugin Details

Severity: High

ID: 365394

File Name: ubuntu_USN-8699-1.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 10/13/2026

Updated: 10/13/2026

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

Risk Information

VPR

Risk Factor: Medium

Score: 5

Percentile: 93.19

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:canonical:ubuntu_linux:22.04:-:lts, cpe:/o:canonical:ubuntu_linux:24.04:-:lts, cpe:/o:canonical:ubuntu_linux:26.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:libssh-4, p-cpe:/a:canonical:ubuntu_linux:libssh-gcrypt-4

Required KB Items: Host/cpu, Host/Debian/dpkg-l, Host/Ubuntu, Host/Ubuntu/release

Exploit Ease: No known exploits are available

Patch Publication Date: 8/31/2026

Vulnerability Publication Date: 7/21/2026

Reference Information

CVE: CVE-2026-15370, CVE-2026-59843, CVE-2026-59844, CVE-2026-59845, CVE-2026-59846, CVE-2026-59847, CVE-2026-59848, CVE-2026-59849, CVE-2026-59850

USN: 8699-1