How severe is CVE-2020-26117?

CVE-2020-26117 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2020-26117 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-26117?

CVE-2020-26117 primarily affects Tigervnc. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-26117?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-26117 published?

CVE-2020-26117 was published on 2020-09-27 and last updated on 2026-06-17.

CVE-2020-26117

CVE-2020-26117 is a high-severity vulnerability in Tigervnc with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-295.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 5.8
EPSS exploit prediction: 3% (86th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-295
Affected product: Tigervnc
Published: 2020-09-27
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2020-26117?: CVE-2020-26117 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2020-26117 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-26117?: CVE-2020-26117 primarily affects Tigervnc. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2020-26117?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2020-26117 published?: CVE-2020-26117 was published on 2020-09-27 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:tigervnc:tigervnc:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*

More vulnerabilities in Tigervnc

CVE-2014-0011 — Critical (CVSS 9.8): Multiple heap-based buffer overflows in the ZRLE_DECODE function in common/rfb/zrleDecode.h in TigerVNC before 1.3.1,…
CVE-2017-5581 — Critical (CVSS 9.8): Buffer overflow in the ModifiablePixelBuffer::fillRect function in TigerVNC before 1.7.1 allows remote servers to…
CVE-2014-8241 — Critical (CVSS 9.8): XRegion in TigerVNC allows remote VNC servers to cause a denial of service (NULL pointer dereference) by leveraging…
CVE-2017-7393 — High (CVSS 8.8): In TigerVNC 1.7.1 (VNCSConnectionST.cxx VNCSConnectionST::fence), an authenticated client can cause a double free,…
CVE-2026-34352 — High (CVSS 8.5): In TigerVNC before 1.16.2, Image.cxx in x0vncserver allows other users to observe or manipulate the screen contents, or…
CVE-2025-26601 — High (CVSS 7.8): A use-after-free flaw was found in X.Org and Xwayland. When changing an alarm, the values of the change mask are…

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