CVE-2026-3787 UltraVNC Windows Service cryptbase.dll uncontrolled search path

High 7.3 Published 8 Mar 2026 Updated 10 Mar 2026

Local attackers can exploit an uncontrolled search path in UltraVNC's cryptbase.dll to execute arbitrary code, requiring high complexity and local access.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Local or same network only
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-3787?

CVE-2026-3787 is a high-severity vulnerability in UltraVNC, published on 8 Mar 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

A weakness has been identified in UltraVNC 1.6.4.0 on Windows. This affects an unknown function in the library cryptbase.dll of the component Windows Service. This manipulation causes uncontrolled search path. The attack requires local access. A high degree of complexity is needed for the attack. The exploitability is reported as difficult. The vendor was contacted early about this disclosure but did not respond in any way.

Weakness: CWE-427, CWE-426

Which versions are affected by CVE-2026-3787?

It affects 1 product.

Products include Uvnc Ultravnc.

How do I fix CVE-2026-3787?

No fix has been published for CVE-2026-3787 yet. Limit exposure of the affected software until one is available.

Is CVE-2026-3787 being exploited?

There is no known exploitation of CVE-2026-3787 in the wild and no public exploit code.

Sources

Also known as GHSA-97cv-xr93-496p.