CVE-2018-20021: High severity Libvnc Project Libvncserver vulnerability

Published Dec 19, 2018
·
Updated

Last updated 11 July 2025

Other sources

LibVNC before commit c3115350eb8bb635d0fdb4dbbb0d0541f38ed19c contains a CWE-835: Infinite loop vulnerability in VNC client code. Vulnerability allows attacker to consume excessive amount of resources like CPU and RAM

— Launchpad

Affected Software

11 affected componentsFixes available
Libvnc Project Libvncserver<0.9.12
Canonical Ubuntu Linux=14.04
Canonical Ubuntu Linux=16.04
Canonical Ubuntu Linux=18.04
Canonical Ubuntu Linux=18.10
Debian Debian Linux=8.0
Debian Debian Linux=9.0
debian/libvncserver
0.9.13+dfsg-2+deb11u10.9.14+dfsg-1+deb12u10.9.15+dfsg-1+deb13u10.9.15+dfsg-6
debian/ssvnc
1.0.29-51.0.29-61.0.29-6.11.0.29-7
debian/tightvnc
1:1.3.10-31:1.3.10-71:1.3.10-91:1.3.10-11
debian/veyon
4.5.3+repack1-14.7.5+repack1-14.9.5+repack1-24.9.7+repack1-1.1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade debian/libvncserver to a version that resolves this vulnerability.

    Fixed in 0.9.13+dfsg-2+deb11u1Fixed in 0.9.14+dfsg-1+deb12u1Fixed in 0.9.15+dfsg-1+deb13u1Fixed in 0.9.15+dfsg-6
  2. Upgrade

    Upgrade debian/ssvnc to a version that resolves this vulnerability.

    Fixed in 1.0.29-5Fixed in 1.0.29-6Fixed in 1.0.29-6.1Fixed in 1.0.29-7
  3. Upgrade

    Upgrade debian/tightvnc to a version that resolves this vulnerability.

    Fixed in 1:1.3.10-3Fixed in 1:1.3.10-7Fixed in 1:1.3.10-9Fixed in 1:1.3.10-11
  4. Upgrade

    Upgrade debian/veyon to a version that resolves this vulnerability.

    Fixed in 4.5.3+repack1-1Fixed in 4.7.5+repack1-1Fixed in 4.9.5+repack1-2Fixed in 4.9.7+repack1-1.1
  5. Upgrade

    Upgrade LibVNC to a version that resolves this vulnerability.

    Patch c3115350eb8bb635d0fdb4dbbb0d0541f38ed19c

Event History

Dec 19, 2018
CVE Published
via MITRE·04:00 PM
Data Sourced
via MITRE·04:00 PM
DescriptionWeakness
Data Sourced
via NVD·04:29 PM
DescriptionSeverityWeaknessAffected Software
Jan 11, 2024
Data Sourced
via Launchpad·10:58 PM
Description
Feb 19, 2026
Data Sourced
via Ubuntu·07:59 PM
RemedyDescriptionSeverityAffected Software
Jul 5, 2026
Data Sourced
via Debian·02:49 AM
DescriptionAffected Software
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Frequently Asked Questions

1

What is the vulnerability ID for this issue?

The vulnerability ID for this issue is CVE-2018-20021.

2

What is the severity of CVE-2018-20021?

The severity of CVE-2018-20021 is high, with a severity value of 7.5.

3

What is the description of CVE-2018-20021?

CVE-2018-20021 is a vulnerability in LibVNC that allows an attacker to consume excessive resources like CPU and RAM due to an infinite loop.

4

Which software versions are affected by CVE-2018-20021?

CVE-2018-20021 affects multiple versions of LibVNC, including 0.9.12 and earlier, 1:3.0.3+dfsg1-3ubuntu0.1 and earlier, and 1:2.0.2+dfsg1-2+ and earlier.

5

Is there a fix available for CVE-2018-20021?

Yes, a fix for CVE-2018-20021 is available. Users should update to commit c3115350eb8bb635d0fdb4dbbb0d0541f38ed19c or a later version of LibVNC.

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