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Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : LibVNCServer vulnerabilities (USN-8463-1)

medium Nessus Plugin ID 322481

Synopsis

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

Description

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8463-1 advisory.

 It was discovered that LibVNCServer had a memory leak in the client cleanup function. An attacker could possibly use this issue to cause LibVNCServer to consume memory, leading to a denial of service. This issue only affected Ubuntu 22.04 LTS. (CVE-2020-29260)

 It was discovered that LibVNCServer did not properly validate bounds when handling UltraZip encoding subrectangles. A remote attacker could possibly use this issue to obtain sensitive information or cause a denial of service. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 25.04.
 (CVE-2026-32853)

 It was discovered that LibVNCServer did not properly validate return values in the HTTP proxy handlers. A remote attacker could possibly use this issue to cause LibVNCServer to crash, resulting in a denial of service. This issue only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 25.04. (CVE-2026-32854)

 It was discovered that LibVNCServer did not properly handle Tight encoding gradient filter rectangles. A remote attacker could use this issue to cause LibVNCServer to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2026-44988)

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 libvncclient1, libvncserver-dev and / or libvncserver1 packages.

See Also

https://ubuntu.com/security/notices/USN-8463-1

Plugin Details

Severity: Medium

ID: 322481

File Name: ubuntu_USN-8463-1.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 6/24/2026

Updated: 6/24/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 6.7

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 7.4

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

CVSS Score Source: CVE-2026-32853

CVSS v3

Risk Factor: High

Base Score: 8.1

Temporal Score: 7.3

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

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

CVSS v4

Risk Factor: Medium

Base Score: 6.9

Threat Score: 5.5

Threat Vector: CVSS:4.0/E:P

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

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/Debian/dpkg-l, Host/Ubuntu, Host/Ubuntu/release

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 6/23/2026

Vulnerability Publication Date: 9/2/2022

Reference Information

CVE: CVE-2020-29260, CVE-2026-32853, CVE-2026-32854, CVE-2026-44988

USN: 8463-1