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CVE-2018-20020

34
FAUCET Score

CVE-2018-20020 is a critical heap out-of-bounds write vulnerability in LibVNC client code (before commit 7b1ef0ffc4815cab9a96c7278394152bdc89dc4d) that affects various Canonical and Debian Linux distributions. This flaw, rated 9.8 CVSS, allows unauthenticated attackers to achieve remote code execution with low attack complexity. While no public exploit code or active exploitation has been observed, the vulnerability has garnered significant community discussion and media coverage, indicating its potential impact.

Impacted Technologies

VendorProductVersion(s)CPE
< 0.9.12CPE matchmatch criteria
cpe:2.3:a:libvnc_project:libvncserver:*:*:*:*:*:*:*:*
14.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
16.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
18.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
18.10CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:18.10:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
8.62%
Probability of exploitation in next 30 days
EPSS Percentile
94.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0862 is in the 90th percentile among its peer group of 36,833 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (3)

redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: libvncserver
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: libvncserver
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: libvncserver

Vendor Advisories (1)

redhatCVE-2018-20020Moderate

libvncserver: Heap out-of-bound write inside structure in VNC client code allows for potential code execution

Dec 19, 2018

References

ics-cert.kaspersky.com / advisories/klcert-advisories/2018/12/19/klcert-18-030-libvnc-heap-out-of-bound-write
Third Party Advisory
lists.debian.org / debian-lts-announce/2018/12/msg00017.html
Mailing ListThird Party Advisory
lists.debian.org / debian-lts-announce/2019/10/msg00042.html
lists.debian.org / debian-lts-announce/2019/11/msg00033.html
security.gentoo.org / glsa/201908-05
security.gentoo.org / glsa/202006-06
usn.ubuntu.com / 3877-1
Third Party Advisory
usn.ubuntu.com / 4547-1
usn.ubuntu.com / 4547-2
usn.ubuntu.com / 4587-1
debian.org / security/2019/dsa-4383
Third Party Advisory