Buffer Overflow Vulnerability in UltraVNC Repeater by UltraVNC

CVE-2026-7840

What is CVE-2026-7840?

The UltraVNC Repeater prior to 1.8.2.2 contains a vulnerability that allows an unauthenticated attacker to exploit a buffer overflow in its embedded HTTP administration server. The functions responsible for handling HTTP requests write user-supplied URIs into a fixed-size buffer without adequate bounds checking, leading to a situation where an attacker can send a crafted request containing an excessively long URI. This overflow can corrupt memory and potentially allow the attacker to execute arbitrary code on the server, posing a significant security threat.

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