CVE-2018-20023

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

Published: 2018-12-19 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2018-20023 is rated Moderate Risk (60.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 2.50%). EPSS rose +1.64% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2018-20023

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.86% 2.50% +1.64%
2 2025-12-28 1.14% 0.86% -0.28%
3 2025-12-27 — 1.14% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2018-20023

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.0 HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2018-20023

OS Trackers for CVE-2018-20023

vendor priority summary link
alpine high CVE-2018-20023: 1 source package rows (libvncserver); 4 state rows across 2 repos (3.22-community, edge-community); fixed 0, open 4. https://security.alpinelinux.org/vuln/CVE-2018-20023
debian not yet assigned CVE-2018-20023 not yet assigned priority: Debian including 2 source packages (libvncserver, veyon), 10 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 10. https://security-tracker.debian.org/tracker/CVE-2018-20023
gentoo normal CVE-2018-20023: 1 GLSA(s) (201908-05), 1 atom(s) (net-libs/libvncserver); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2018-20023
redhat low — https://access.redhat.com/security/cve/CVE-2018-20023
suse medium CVE-2018-20023 severity moderate: SUSE including 22 source package names (LibVNCServer, LibVNCServer-devel, …), 86 product×package rows across 53 product lines (SLES for SAP Applications 11 SP3, SUSE Enterprise Storage 4, … (53 product lines)): Fixed 79, Known Not Affected 7. https://www.suse.com/security/cve/CVE-2018-20023/
ubuntu medium CVE-2018-20023 medium priority: Ubuntu including 3 source packages (italc, libvncserver, x11vnc), 19 status rows across 7 suites (bionic, cosmic, disco, focal, trusty, upstream, xenial): released 8, not-affected 7, DNE 2, ignored 1, needs-triage 1. https://ubuntu.com/security/CVE-2018-20023

Affected software / configurations for CVE-2018-20023

Vendor Product Version Raw CPE
libvnc_project libvncserver < 0.9.12 cpe:2.3:a:libvnc_project:libvncserver:*:*:*:*:*:*:*:*
debian debian_linux 8.0 cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
canonical ubuntu_linux 14.04 cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 16.04 cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 18.04 cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 18.10 cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*

References for CVE-2018-20023

cvelogic Threat Intelligence