CVE-2020-26117

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.

Published: 2020-09-27 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-26117 is rated Moderate Risk (62.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 3.06%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2020-26117

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-22 3.02% 3.06% +0.04%
2 2026-06-15 0.69% 3.02% +2.33%
3 2026-04-14 — 0.69% —

Full EPSS history (19 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-26117

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.1 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 5.2 [email protected]
5.8 2.0 MEDIUM
AV:N/AC:M/Au:N/C:P/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 8.6 4.9 [email protected]

Weakness enumeration for CVE-2020-26117

OS Trackers for CVE-2020-26117

vendor priority summary link
debian not yet assigned CVE-2020-26117 not yet assigned priority: Debian including 1 source packages (tigervnc), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2020-26117
gentoo normal CVE-2020-26117: 1 GLSA(s) (202407-14), 1 atom(s) (net-misc/tigervnc); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2020-26117
redhat medium — https://access.redhat.com/security/cve/CVE-2020-26117
suse critical CVE-2020-26117 severity critical: SUSE including 306 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 440 product×package rows across 70 product lines (HPE Helion OpenStack 8, Image SLES12-SP5-Azure-SAP-BYOS, … (70 product lines)): Known Affected 231, Fixed 209. https://www.suse.com/security/cve/CVE-2020-26117/
ubuntu medium CVE-2020-26117 medium priority: Ubuntu including 1 source packages (tigervnc), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 10, DNE 2, released 2, ignored 1, needs-triage 1. https://ubuntu.com/security/CVE-2020-26117

Affected software / configurations for CVE-2020-26117

Vendor Product Version Raw CPE
tigervnc tigervnc < 1.11.0 cpe:2.3:a:tigervnc:tigervnc:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
opensuse leap 15.2 cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*

References for CVE-2020-26117

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2020-10/msg00025.html Broken Link Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00024.html Broken Link Mailing List Third Party Advisory
https://bugzilla.opensuse.org/show_bug.cgi?id=1176733 Issue Tracking Third Party Advisory
https://github.com/TigerVNC/tigervnc/commit/20dea801e747318525a5859fe4f37c52b05310cb Patch Third Party Advisory
https://github.com/TigerVNC/tigervnc/commit/7399eab79a4365434d26494fa1628ce1eb91562b Patch Third Party Advisory
https://github.com/TigerVNC/tigervnc/commit/b30f10c681ec87720cff85d490f67098568a9cba Patch Third Party Advisory
https://github.com/TigerVNC/tigervnc/commit/f029745f63ac7d22fb91639b2cb5b3ab56134d6e Patch Third Party Advisory
https://github.com/TigerVNC/tigervnc/releases/tag/v1.11.0 Release Notes Third Party Advisory
https://lists.debian.org/debian-lts-announce/2020/10/msg00007.html Mailing List Third Party Advisory
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