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Vulnerabilities

Vulnerability · CVE-2020-37134

UltraVNC Viewer 1.2.4.0 contains a denial of service vulnerability that allows attackers to crash the application by manipulating VNC Server input.

Published Feb 5, 2026 · catalog updated Mar 5, 2026 · UltraVNC Team UltraVNC Viewer

Last checked Nov 4, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2020-37134. EPSS is 0.40%. Act only if a listed version of UltraVNC Team UltraVNC Viewer is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium4.6
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.40%
Remediation
Vendor / distro source
Affected products
vendor UltraVNC Team UltraVNC Viewer 1.2.4.0

UltraVNC Viewer 1.2.4.0 contains a denial of service vulnerability that allows attackers to crash the application by manipulating VNC Server input. Attackers can generate a malformed 256-byte payload and paste it into the VNC Server connection dialog to trigger an application crash.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor UltraVNC Team UltraVNC Viewer 1.2.4.01.2.4.0

How to fix CVE-2020-37134

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2020-37134. EPSS is 0.40%. Act only if a listed version of UltraVNC Team UltraVNC Viewer is installed.

Which versions are affected?

Compare what you have installed with UltraVNC Team UltraVNC Viewer 1.2.4.0 1.2.4.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.40%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 5, 2026 · EUVD

    Detected

    UltraVNC Viewer 1.2.4.0 contains a denial of service vulnerability that allows attackers to crash the application by manipulating VNC Server input. Attackers can generate a malformed 256-byte payload and paste it into the VNC Server connection dialog to trigger an application crash.

  2. Mar 5, 2026 · EUVD

    Updated

    UltraVNC Viewer 1.2.4.0 contains a denial of service vulnerability that allows attackers to crash the application by manipulating VNC Server input. Attackers can generate a malformed 256-byte payload and paste it into the VNC Server connection dialog to trigger an application crash.

Sources

  • CVE.orgVulnerability recordCVE-2020-37134

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2020-37134

    30-day exploitation probability 0.40%

    first.org
  • EUVDVulnerability recordEUVD-2020-31034

    UltraVNC Viewer 1.2.4.0 contains a denial of service vulnerability that allows attackers to crash the application by manipulating VNC Server input. Attackers can generate a malformed 256-byte payload and paste it into the VNC Server connection dialog to trigger an application cra

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Nov 3, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgNov 4, 2026
  • FIRST EPSSNov 3, 2026
  • EUVDNov 2, 2026