CVE-2018-20023

Severity: high (CVSS 7.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2018-12-19 · updated 2026-06-17
Weakness: CWE-665

Description

LibVNC before 8b06f835e259652b0ff026898014fc7297ade858 contains CWE-665: Improper Initialization vulnerability in VNC Repeater client code that allows attacker to read stack memory and can be abuse for information disclosure. Combined with another vulnerability, it can be used to leak stack memory layout and in bypassing ASLR

Affected products

Canonical Ubuntu Linux: 14.04, 16.04, 18.04, 18.10
Debian Linux: 8.0, 9.0
Libvnc Project Libvncserver: before 0.9.12 — fixed in 0.9.12

How to fix

Upgrade to a fixed version: Libvnc Project Libvncserver 0.9.12. Check the vendor advisory for mitigations.

References

https://ics-cert.kaspersky.com/advisories/klcert-advisories/2018/12/19/klcert-18-033-libvnc-memory-leak/
https://lists.debian.org/debian-lts-announce/2018/12/msg00017.html
https://lists.debian.org/debian-lts-announce/2019/10/msg00042.html
https://security.gentoo.org/glsa/201908-05
https://usn.ubuntu.com/3877-1/
https://usn.ubuntu.com/4547-1/
https://usn.ubuntu.com/4587-1/
https://www.debian.org/security/2019/dsa-4383
https://ics-cert.kaspersky.com/advisories/klcert-advisories/2018/12/19/klcert-18-033-libvnc-memory-leak/
https://lists.debian.org/debian-lts-announce/2018/12/msg00017.html
https://lists.debian.org/debian-lts-announce/2019/10/msg00042.html
https://security.gentoo.org/glsa/201908-05

Get alerted when CVE-2018-20023 or the next vulnerability affects your stack