CVE-2020-37134

HIGH

UltraVNC Viewer 1.2.4.0 - Denial of Service via Malformed VNC Server Input

Title source: llm
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2020-37134. PoCs published by chuyreds.

AI-analyzed exploit summary This PoC exploits a denial-of-service vulnerability in UltraVNC Viewer 1.2.4.0 by sending a malformed VNC server string with 256 'A' characters, causing the application to crash upon connection attempt.

Description

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.

Exploits (1)

exploitdb WORKING POC
by chuyreds · pythondoswindows
https://www.exploit-db.com/exploits/48291

This PoC exploits a denial-of-service vulnerability in UltraVNC Viewer 1.2.4.0 by sending a malformed VNC server string with 256 'A' characters, causing the application to crash upon connection attempt.

Classification
Working Poc 90%
Attack Type
Dos
Complexity
Trivial
Reliability
Reliable
Target: UltraVNC Viewer 1.2.4.0
No auth needed
Prerequisites: UltraVNC Viewer 1.2.4.0 installed on Windows · Ability to paste malicious input into the VNC Server field
devstral-2 · analyzed Feb 16, 2026 Full analysis →

References (3)

Core 3
Core References
Exploit, Third Party Advisory exploit
https://www.exploit-db.com/exploits/48291
Various Sources product
https://www.uvnc.com/

Scores

CVSS v3 7.5
EPSS 0.0036
EPSS Percentile 27.8%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CISA SSVC

Vulnrichment
Exploitation poc
Automatable yes
Technical Impact partial

Details

CWE
CWE-770
Status published
Products (1)
UltraVNC Team/UltraVNC Viewer 1.2.4.0
Published Feb 05, 2026
Tracked Since Feb 18, 2026