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Fencer Vulns
critical 9.8

CVE-2017-18922 json

It was discovered that websockets.c in LibVNCServer prior to 0.9.12 did not properly decode certain WebSocket frames.

published 2020-06-30 6 y ago modified 2026-06-17 4 mo ago also EUVD-2017-10012

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.3%
EPSS 2.3% chance of exploitation in 30 days, percentile 83%
public exploits
0
none known

Summary

It was discovered that websockets.c in LibVNCServer prior to 0.9.12 did not properly decode certain WebSocket frames. A malicious attacker could exploit this by sending specially crafted WebSocket frames to a server, causing a heap-based buffer overflow.

Patch / fix

  • libvncserver_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
  • libvncserver Debian 14, Debian 13, Debian 12 0.9.12+dfsg-3

debian advisories DEBIAN-CVE-2017-18922

  • libvncserver Ubuntu 16.04 LTS 0.9.10+dfsg-3ubuntu0.16.04.4
  • libvncserver Ubuntu 18.04 LTS 0.9.11+dfsg-1ubuntu1.2
  • libvncserver Ubuntu 20.04 LTS 0.9.12+dfsg-9ubuntu0.1

ubuntu advisories UBUNTU-CVE-2017-18922

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 RHEL 8 0.9.11-15.el8_2.1
  • libvncserver RHEL 7 0.9.9-14.el7_8.1
  • libvncserver RHEL 8.0 E4S 0.9.11-9.el8_0.3
  • libvncserver RHEL 8.1 EUS 0.9.11-9.el8_1.3

red hat advisories RHSA-2020:3588RHSA-2020:3456RHSA-2020:3385RHSA-2020:3281

  • LibVNCServer SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES for SAP 12 SP3 +15 more 0.9.9-17.31.1
  • LibVNCServer SLE Workstation Extension 15 SP2, SLE Workstation Extension 15 SP1, SLE Module for Package Hub 15 SP2 +1 more 0.9.10-4.22.1
  • LibVNCServer SLE Workstation Extension 15 SP2, SLE Workstation Extension 15 SP1, SLE Module for Package Hub 15 SP2 +1 more 0.9.10-4.19.1

suse advisories SUSE-SU-2020:2167-1SUSE-SU-2020:1922-1SUSE-SU-2020:1873-1

  • LibVNCServer openSUSE Leap 15.2 0.9.10-lp152.9.4.2
  • LibVNCServer openSUSE Leap 15.2 0.9.10-lp152.9.8.1
  • LibVNCServer openSUSE Leap 15.1 0.9.10-lp151.7.9.1
  • LibVNCServer openSUSE Leap 15.2 0.9.10-lp152.9.4.1
  • LibVNCServer openSUSE Leap 15.1 0.9.10-lp151.7.6.1

opensuse advisories openSUSE-SU-2020:1056-1openSUSE-SU-2020:1025-1openSUSE-SU-2020:0988-1openSUSE-SU-2020:0978-1openSUSE-SU-2020:0960-1

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-2017-18922 updated cvss 9.8

libvncserver: websocket decoding buffer overflow

  • Red Hat CodeReady Linux Builder (v. 8) libvncserver 0.9.11-15.el8_2.1
    fixed: vendor fix RHSA-2020:3385
  • Red Hat CodeReady Linux Builder EUS (v. 8.1) libvncserver 0.9.11-9.el8_1.3
    fixed: vendor fix RHSA-2020:3456
  • Red Hat Enterprise Linux AppStream (v. 8) libvncserver 0.9.11-15.el8_2.1
    fixed: vendor fix RHSA-2020:3385
  • Red Hat Enterprise Linux AppStream E4S (v. 8.0) libvncserver 0.9.11-9.el8_0.3
    fixed: vendor fix RHSA-2020:3588
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) libvncserver 0.9.11-9.el8_1.3
    fixed: vendor fix RHSA-2020:3456
  • Red Hat Enterprise Linux Client (v. 7) libvncserver 0.9.9-14.el7_8.1 Red Hat Enterprise Linux Client Optional (v. 7) libvncserver-devel 0.9.9-14.el7_8.1, libvncserver-debuginfo 0.9.9-14.el7_8.1 Red Hat Enterprise Linux Server (v. 7) libvncserver 0.9.9-14.el7_8.1 Red Hat Enterprise Linux Server Optional (v. 7) libvncserver-devel 0.9.9-14.el7_8.1, libvncserver-debuginfo 0.9.9-14.el7_8.1 Red Hat Enterprise Linux Workstation (v. 7) libvncserver 0.9.9-14.el7_8.1 Red Hat Enterprise Linux Workstation Optional (v. 7) libvncserver-devel 0.9.9-14.el7_8.1, libvncserver-debuginfo 0.9.9-14.el7_8.1
    fixed: vendor fix RHSA-2020:3281
  • Red Hat Enterprise Linux 6 libvncserver
    not affected: vulnerable code not present

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

2.26% chance of exploitation in the next 30 days, higher than 83% of all scored CVEs (FIRST EPSS, 2026-11-08).

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.