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Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : LibVNCServer vulnerability (USN-8494-1)

critical Nessus Plugin ID 325014

Synopsis

The remote Ubuntu host is missing a security update.

Description

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-8494-1 advisory.

 It was discovered that LibVNCServer incorrectly handled the Tight decoder in libvncclient. A remote attacker could use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly execute arbitrary code.

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

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

Solution

Update the affected libvncclient1, libvncserver-dev and / or libvncserver1 packages.

See Also

https://ubuntu.com/security/notices/USN-8494-1

Plugin Details

Severity: Critical

ID: 325014

File Name: ubuntu_USN-8494-1.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 7/3/2026

Updated: 7/3/2026

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: 4.9

Percentile: 57.99

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 5.5

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

CVSS Score Source: CVE-2026-50538

CVSS v3

Risk Factor: Critical

Base Score: 9.8

Temporal Score: 8.5

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

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

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:25.10, cpe:/o:canonical:ubuntu_linux:24.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:libvncserver-dev, p-cpe:/a:canonical:ubuntu_linux:libvncserver1, cpe:/o:canonical:ubuntu_linux:22.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:libvncclient1, cpe:/o:canonical:ubuntu_linux:26.04:-:lts

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

Exploit Ease: No known exploits are available

Patch Publication Date: 7/2/2026

Vulnerability Publication Date: 7/2/2026

Reference Information

CVE: CVE-2026-50538

USN: 8494-1