CVE-2019-25600

MEDIUM

UltraVNC Viewer 1.2.2.4 Denial of Service via Buffer Overflow

Title source: cna
STIX 2.1

Exploitation Summary

EIP tracks 1 public exploit for CVE-2019-25600. PoCs published by Victor Mondragón.

AI-analyzed exploit summary This PoC exploits a buffer overflow vulnerability in UltraVNC Viewer 1.2.2.4 by writing a 256-byte string of 'A' characters to a file, which when pasted into the VNC Server field and connected, causes a denial of service (crash).

Description

UltraVNC Viewer 1.2.2.4 contains a denial of service vulnerability that allows attackers to crash the application by supplying an oversized string to the VNC Server input field. Attackers can paste a malicious string containing 256 repeated characters into the VNC Server field and click Connect to trigger a buffer overflow that crashes the viewer.

Exploits (1)

exploitdb WORKING POC
by Victor Mondragón · pythondoswindows
https://www.exploit-db.com/exploits/46702

This PoC exploits a buffer overflow vulnerability in UltraVNC Viewer 1.2.2.4 by writing a 256-byte string of 'A' characters to a file, which when pasted into the VNC Server field and connected, causes a denial of service (crash).

Classification
Working Poc 90%
Attack Type
Dos
Complexity
Trivial
Reliability
Reliable
Target: UltraVNC Viewer 1.2.2.4
No auth needed
Prerequisites: Python environment · UltraVNC Viewer installed on target system
devstral-2 · analyzed Mar 22, 2026 Full analysis →

References (4)

Core 4
Core References
Exploit exploit
ExploitDB-46702
https://www.exploit-db.com/exploits/46702
Product product
Official Product Homepage
https://www.uvnc.com/
Third Party Advisory third-party-advisory
VulnCheck Advisory: UltraVNC Viewer 1.2.2.4 Denial of Service via Buffer Overflow
https://www.vulncheck.com/advisories/ultravnc-viewer-denial-of-service-via-buffer-overflow

Scores

CVSS v3 6.5
EPSS 0.0069
EPSS Percentile 47.8%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

CISA SSVC

Vulnrichment
Exploitation poc
Automatable yes
Technical Impact partial

Details

CWE
CWE-787
Status published
Products (1)
Uvnc/UltraVNC Viewer 1.2.2.4
Published Mar 22, 2026
Tracked Since Mar 22, 2026