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Fencer Vulns
critical 9.8

CVE-2018-20748 json

LibVNC before 0.9.12 contains multiple heap out-of-bounds write vulnerabilities in libvncclient/rfbproto.c.

published 2019-01-30 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-13291

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.3%
EPSS 3.3% chance of exploitation in 30 days, percentile 88%
public exploits
0
none known

Summary

LibVNC before 0.9.12 contains multiple heap out-of-bounds write vulnerabilities in libvncclient/rfbproto.c. The fix for CVE-2018-20019 was incomplete.

Patch / fix

  • libvnc_project libvncserver 0.9.12
  • siemens simatic_itc1500_firmware 3.2.1.0
  • siemens simatic_itc1500_pro_firmware 3.2.1.0
  • siemens simatic_itc1900_firmware 3.2.1.0
  • siemens simatic_itc1900_pro_firmware 3.2.1.0
  • siemens simatic_itc2200_firmware 3.2.1.0
  • siemens simatic_itc2200_pro_firmware 3.2.1.0
  • veyon Debian 13, Debian 12 4.1.7+repack1-1
  • libvncserver Debian 14, Debian 13, Debian 12 0.9.11+dfsg-1.3

debian advisories DEBIAN-CVE-2018-20748

  • italc Ubuntu 16.04 LTS 1:2.0.2+dfsg1-4ubuntu0.1
  • italc Ubuntu 18.04 LTS 1:3.0.3+dfsg1-3ubuntu0.1
  • libvncserver Ubuntu 14.04 LTS 0.9.9+dfsg-1ubuntu1.4
  • libvncserver Ubuntu 16.04 LTS 0.9.10+dfsg-3ubuntu0.16.04.3
  • libvncserver Ubuntu 18.04 LTS 0.9.11+dfsg-1ubuntu1.1
  • tightvnc Ubuntu Pro 14.04 LTS 1.3.9-6.5+deb8u1build0.14.04.1~esm1

ubuntu advisories UBUNTU-CVE-2018-20748

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • LibVNCServer SLES 12 SP4, SLES 12 SP3, SLES 12 SP2-BCL +11 more 0.9.9-17.11.1
  • LibVNCServer SLES for SAP 11 SP4, SLES 11 SP4, SLE Software Development Kit 11 SP4 +1 more 0.9.1-160.9.1
  • LibVNCServer SLE Workstation Extension 15, SLE Module for Package Hub 15 0.9.10-4.6.1

suse advisories SUSE-SU-2019:0313-2SUSE-SU-2019:13952-1SUSE-SU-2019:0313-1SUSE-SU-2019:0283-1

  • LibVNCServer openSUSE Leap 15.0 0.9.10-lp150.3.6.1

opensuse advisories openSUSE-SU-2019:0196-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-20748 updated cvss 8.8

libvncserver: Multiple heap out-of-bound writes in VNC client code (Incomplete fix for CVE-2018-20019)

  • Red Hat Enterprise Linux 6 libvncserver
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise Linux 7 libvncserver Red Hat Enterprise Linux 8 libvncserver
    affected: no fix available

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-21-350-12 updated cvss 9.8

Siemens SIMATIC ITC

  • Siemens SIMATIC ITC1500 V3 <V3.2.1.0 Siemens SIMATIC ITC1500 V3 PRO <V3.2.1.0 Siemens SIMATIC ITC1900 V3 <V3.2.1.0 Siemens SIMATIC ITC1900 V3 PRO <V3.2.1.0 Siemens SIMATIC ITC2200 V3 <V3.2.1.0 Siemens SIMATIC ITC2200 V3 PRO <V3.2.1.0
    affected: fixed in V3.2.1.0, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

3.32% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • openwall.com https://www.openwall.com/lists/oss-security/2018/12/10/8 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.