Denial of Service Vulnerability in UltraVNC Viewer by UltraVNC
CVE-2020-37134

4.6MEDIUM

Key Information:

Vendor

Ultravnc Team

Status
Ultravnc Viewer
Vendor
CVE Published:
5 February 2026

Badges

👾 Exploit Exists🟡 Public PoC

What is CVE-2020-37134?

UltraVNC Viewer 1.2.4.0 is susceptible to a denial of service flaw that enables attackers to compromise the application's stability. By crafting a malformed 256-byte payload and inserting it into the VNC Server connection dialog, an attacker can induce an application crash, disrupting service continuity and user experience. This vulnerability highlights the importance of securing remote access software from potential manipulation that could lead to service disruptions.

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Deploy the Patch

Affected Version(s)

UltraVNC Viewer 1.2.4.0

Exploit Proof of Concept (PoC)

PoC code is written by security researchers to demonstrate the vulnerability can be exploited. PoC code is also a key component for weaponization which could lead to ransomware.

CVE-2020-37134 - Proof of Concept

References

https://www.exploit-db.com/exploits/48291
exploit
https://www.uvnc.com/
product
https://www.vulncheck.com/advisories/ultravnc-viewer-vncs...
third-party-advisory

CVSS V4

Score:
4.6
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
Low
Attack Vector:
Local
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • 🟡

    Public PoC available

  • 👾

    Exploit known to exist

  • Vulnerability published

  • Vulnerability Reserved

Credit

chuyreds
JSON
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