Skip to content
Fencer Vulns
high 8.1

CVE-2020-26117 json

In rfb/CSecurityTLS.cxx and rfb/CSecurityTLS.java in TigerVNC before 1.11.0, viewers mishandle TLS certificate exceptions.

published 2020-09-27 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-18747

cvss
8.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.1%
EPSS 3.1% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

In rfb/CSecurityTLS.cxx and rfb/CSecurityTLS.java in TigerVNC before 1.11.0, viewers mishandle TLS certificate exceptions. They store the certificates as authorities, meaning that the owner of a certificate could impersonate any server after a client had added an exception.

Patch / fix

  • tigervnc tigervnc 1.11.0
  • tigervnc Debian 14, Debian 13, Debian 12 1.10.1+dfsg-9

debian advisories DEBIAN-CVE-2020-26117

  • tigervnc Ubuntu Pro 20.04 LTS 1.10.1+dfsg-3ubuntu0.1+esm2

ubuntu advisories UBUNTU-CVE-2020-26117

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

  • tigervnc RHEL 8 1.11.0-6.el8
  • tigervnc-icons RHEL 8 1.11.0-6.el8
  • tigervnc-server RHEL 8 1.11.0-6.el8
  • tigervnc-license RHEL 8 1.11.0-6.el8
  • tigervnc-selinux RHEL 8 1.11.0-6.el8
  • tigervnc-server-module RHEL 8 1.11.0-6.el8
  • tigervnc-server-minimal RHEL 8 1.11.0-6.el8

red hat advisories RHSA-2021:1783

  • tigervnc SLES for SAP 12 SP3, SLES for SAP 12 SP2, SLES 12 SP3-LTSS +8 more 1.6.0-27.1
  • tigervnc SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 1.8.0-13.14.1
  • tigervnc SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES 12 SP5 +3 more 1.6.0-22.17.1
  • tigervnc SLE Module for Desktop Applications 15 SP2, SLE Module for Desktop Applications 15 SP1, SLE Module for Basesystem 15 SP2 +1 more 1.9.0-19.9.1

suse advisories SUSE-SU-2020:2898-1SUSE-SU-2020:2882-1SUSE-SU-2020:2881-1SUSE-SU-2020:2880-1

  • tigervnc openSUSE Tumbleweed 1.10.1-17.1
  • tigervnc openSUSE Leap 15.1 1.9.0-lp151.4.9.1
  • tigervnc openSUSE Leap 15.2 1.9.0-lp152.7.3.1

opensuse advisories openSUSE-SU-2024:10591-1openSUSE-SU-2020:1841-1openSUSE-SU-2020:1666-1

  • tigervnc Rocky Linux 8 1.11.0-6.el8

rocky linux advisories RLSA-2021:1783

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-2020-26117 updated cvss 8.1

tigervnc: certificate exceptions stored as authorities

  • Red Hat Enterprise Linux 6 tigervnc, tigervnc-server, tigervnc-server-applet, tigervnc-server-module Red Hat Enterprise Linux 7 tigervnc, tigervnc-icons, tigervnc-server, tigervnc-license, tigervnc-server-applet, tigervnc-server-module, +1 more
    affected: workaround, no fix planned “This flaw can be mitigated by not making certificate exceptions in the affected versions of tigervnc, and therefore they will not be stored as authorities.”
  • Red Hat Enterprise Linux AppStream (v. 8) tigervnc 1.11.0-6.el8, tigervnc-icons 1.11.0-6.el8, tigervnc-server 1.11.0-6.el8, tigervnc-license 1.11.0-6.el8, tigervnc-selinux 1.11.0-6.el8, tigervnc-server-module 1.11.0-6.el8, +1 more
    fixed: vendor fix “This flaw can be mitigated by not making certificate exceptions in the affected versions of tigervnc, and therefore they will not be stored as authorities.” RHSA-2021:1783

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

3.06% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
NVD 2.0 5.8 AV:N/AC:M/Au:N/C:P/I:P/A:N

Classification

Weakness
  • CWE-295 Improper Certificate Validation

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.