Skip to content
Fencer Vulns
high 7.5

CVE-2020-25708 json

A divide by zero issue was found to occur in libvncserver-0.9.12.

published 2020-11-27 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-18363

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 74%
public exploits
0
none known

Summary

A divide by zero issue was found to occur in libvncserver-0.9.12. A malicious client could use this flaw to send a specially crafted message that, when processed by the VNC server, would lead to a floating point exception, resulting in a denial of service.

Patch / fix

  • libvncserver Debian 14, Debian 13, Debian 12 0.9.13+dfsg-1

debian advisories DEBIAN-CVE-2020-25708

  • vino Ubuntu 16.04 LTS 3.8.1-0ubuntu9.4
  • vino Ubuntu 18.04 LTS 3.22.0-3ubuntu1.2
  • vino Ubuntu 20.04 LTS 3.22.0-5ubuntu2.2
  • vino Ubuntu 24.04 LTS, Ubuntu 22.04 LTS 3.22.0-6ubuntu3
  • libvncserver Ubuntu 16.04 LTS 0.9.10+dfsg-3ubuntu0.16.04.6
  • libvncserver Ubuntu 18.04 LTS 0.9.11+dfsg-1ubuntu1.4
  • libvncserver Ubuntu 20.04 LTS 0.9.12+dfsg-9ubuntu0.3

ubuntu advisories UBUNTU-CVE-2020-25708

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 0.9.9-17.34.1
  • LibVNCServer SLES 11 SP4-LTSS, SLE Point of Sale 11 SP3 0.9.1-160.22.1
  • LibVNCServer SLE Workstation Extension 15 SP2, SLE Workstation Extension 15 SP1, SLE Module for Package Hub 15 SP2 +1 more 0.9.10-4.25.1

suse advisories SUSE-SU-2020:3550-1SUSE-SU-2020:14549-1SUSE-SU-2020:3515-1

  • LibVNCServer openSUSE Leap 15.1 0.9.10-lp151.7.12.1
  • LibVNCServer openSUSE Leap 15.2 0.9.10-lp152.9.8.1

opensuse advisories openSUSE-SU-2020:2097-1openSUSE-SU-2020:2025-1

  • 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-2020-25708

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

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-2020-25708 updated cvss 7.5

libvncserver: libvncserver/rfbserver.c has a divide by zero which could result in DoS

  • Red Hat Enterprise Linux 6 vino, libvncserver Red Hat Enterprise Linux 7 vino, libvncserver
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 vino
    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 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

Exploit prediction

1.53% chance of exploitation in the next 30 days, higher than 74% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • bugzilla.redhat.com https://bugzilla.redhat.com/show_bug.cgi?id=1896739 referenced PoC, tagged "exploit" by a source, unverified

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

Affected products

  • n/a libvncserver

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.