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Ubuntu 22.04 LTS / 24.04 LTS / 26.04 LTS : OpenSSH vulnerabilities (USN-8533-1)

critical Nessus Plugin ID 326800

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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-8533-1 advisory.

 It was discovered that OpenSSH sftp did not properly constrain the location of downloaded files when connecting to an attacker-controlled server. An attacker could possibly use this issue to write files to unintended locations on the file system. (CVE-2026-59995)

 It was discovered that OpenSSH scp could place files in the parent directory of the intended destination when copying between two remote hosts. An attacker could possibly use this issue to write files to unintended locations. (CVE-2026-59996)

 It was discovered that OpenSSH internal-sftp only recognized the first nine command-line arguments, This could result in certain security-sensitive arguments being ignored, contrary to expectations.
 (CVE-2026-59997)

 It was discovered that OpenSSH had undocumented behaviour regarding the GSSAPIStrictAcceptorCheck option in environments using Windows Active Directory. The documentation has been updated to clarify use of the option. (CVE-2026-59998)

 It was discovered that OpenSSH did not properly enforce precedence of DisableForwarding=yes over PermitTunnel=yes in server configurations. This could possibly result in intended network forwarding restrictions being bypassed, contrary to expectations. (CVE-2026-59999)

 It was discovered that OpenSSH mishandled the MaxAuthTries limit for GSSAPI authentication. A remote attacker could use this issue to perform excessive authentication attempts. (CVE-2026-60000)

 It was discovered that OpenSSH did not always honour the minimum authentication delay. An attacker could possibly use this issue to perform brute-force attacks more efficiently. (CVE-2026-60001)

 It was discovered that the OpenSSH client had a use-after-free vulnerability when a server changed its host key during a key re-exchange. An attacker able to intercept communications could possibly use this issue to execute arbitrary code or obtain sensitive information. (CVE-2026-60002)

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 packages.

See Also

https://ubuntu.com/security/notices/USN-8533-1

Plugin Details

Severity: Critical

ID: 326800

File Name: ubuntu_USN-8533-1.nasl

Version: 1.2

Type: Local

Agent: unix

Published: 7/14/2026

Updated: 7/17/2026

Supported Sensors: Agentless Assessment, Continuous Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Frictionless Assessment Azure, 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: 7.2

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: 8.2

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: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:openssh-client-gssapi, p-cpe:/a:canonical:ubuntu_linux:openssh-client, p-cpe:/a:canonical:ubuntu_linux:openssh-server-gssapi, p-cpe:/a:canonical:ubuntu_linux:openssh-server, p-cpe:/a:canonical:ubuntu_linux:openssh-sftp-server, p-cpe:/a:canonical:ubuntu_linux:openssh-tests, p-cpe:/a:canonical:ubuntu_linux:ssh-askpass-gnome, p-cpe:/a:canonical:ubuntu_linux:ssh

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

Exploit Ease: No known exploits are available

Patch Publication Date: 7/13/2026

Vulnerability Publication Date: 7/8/2026

Reference Information

CVE: CVE-2026-59995, CVE-2026-59996, CVE-2026-59997, CVE-2026-59998, CVE-2026-59999, CVE-2026-60000, CVE-2026-60001, CVE-2026-60002

IAVA: 2026-A-0691

USN: 8533-1