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Fencer Intel
high 7.5

CVE-2019-20839 json

libvncclient/sockets.c in LibVNCServer before 0.9.13 has a buffer overflow via a long socket filename.

published 6y ago modified 4mo ago also EUVD-2019-11376

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.6%
EPSS 3.6% chance of exploitation in 30 days, percentile 89%
public exploits
0
none known

Summary

libvncclient/sockets.c in LibVNCServer before 0.9.13 has a buffer overflow via a long socket filename.

Patch / fix

  • 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 0.9.13+dfsg-1

debian advisories DEBIAN-CVE-2019-20839

  • libvncserver Ubuntu 16.04 LTS 0.9.10+dfsg-3ubuntu0.16.04.5
  • libvncserver Ubuntu 18.04 LTS 0.9.11+dfsg-1ubuntu1.3
  • libvncserver Ubuntu 20.04 LTS 0.9.12+dfsg-9ubuntu0.2

ubuntu advisories UBUNTU-CVE-2019-20839

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 0.9.11-17.el8

red hat advisories RHSA-2021:1811

  • 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

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

  • 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

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

  • libvncserver AlmaLinux 8 0.9.11-17.el8

almalinux advisories ALSA-2021:1811

  • libvncserver Rocky Linux 8 0.9.11-17.el8

rocky linux advisories RLSA-2021:1811

  • libvncserver Alpine 3.24, Alpine 3.23, Alpine 3.22 +10 more 0.9.13-r0

alpine advisories ALPINE-CVE-2019-20839

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Is CVE-2019-20839 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2019-20839 updated cvss 7.5

libvncserver: buffer overflow in ConnectClientToUnixSock()

  • Red Hat Enterprise Linux 7 libvncserver
    affected: no fix planned “Will not fix”
  • Red Hat CodeReady Linux Builder (v. 8) libvncserver-devel 0.9.11-17.el8, libvncserver-debuginfo 0.9.11-17.el8, libvncserver-debugsource 0.9.11-17.el8 Red Hat Enterprise Linux AppStream (v. 8) libvncserver 0.9.11-17.el8
    fixed: vendor fix RHSA-2021:1811
  • 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 7.5

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

3.59% chance of exploitation in the next 30 days, higher than 89% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness
  • CWE-120 Buffer Copy without Checking Size of Input

References

Sources

Fencer Intel 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.