Executive brief
UltraVNC Repeater, a tool used to facilitate remote desktop connections through firewalls, contains a hardcoded administrative password. On new or unmodified installations, an attacker can use this well-known password to log into the web management interface. This allows unauthorized individuals to view active remote support sessions and change security rules, potentially leading to unauthorized access to internal systems.
Technical details
UltraVNC Repeater through 1.8.2.2 contains a hardcoded credential vulnerability (CWE-798) in its HTTP administration interface. In `repeater/webgui/settings.c`, the application initializes the admin password to the literal string "adminadmi2" if the configuration file `settings2.txt` is missing. The HTTP Basic-auth handler, `wi_decode_auth()`, validates this password without implementing rate-limiting or account lockout mechanisms. A remote attacker can exploit this by accessing the repeater's HTTP port (default TCP 80) and authenticating with the default credentials. Successful exploitation grants full administrative access, including the ability to modify allow/deny rules and monitor active sessions. Version 1.8.2.4 appears to be available as a potential update.
Affected products
- UltraVNC UltraVNC Repeater through 1.8.2.2
Timeline
- 2026-07-01: advisory: CVE-2026-7839 published by NVD