Vulnerability Description
UltraVNC repeater through 1.8.2.2 initializes the HTTP administration server with a hardcoded default password. In repeater/webgui/settings.c:197, when settings2.txt is absent on first run the repeater writes the literal string "adminadmi2" as the admin password via strcpy_s(saved_password, 64, "adminadmi2"). The HTTP Basic-auth handler wi_decode_auth() checks this password without rate-limiting or lockout. Any remote attacker who can reach the repeater HTTP port (default TCP 80) can authenticate as administrator using the well-known default credential on a fresh or unmodified installation, gaining full control of the repeater configuration including allow/deny rules and session visibility.
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Uvnc | Ultravnc | <= 1.8.2.2 |
Related Weaknesses (CWE)
References
- https://github.com/ultravnc/UltraVNCProduct
- https://uvnc.com/ProductRelease Notes
- https://www.securin.io/zero-days/cve-2026-7839-hardcoded-default-admin-password-
FAQ
What is CVE-2026-7839?
CVE-2026-7839 is a vulnerability with a CVSS score of 9.1 (CRITICAL). UltraVNC repeater through 1.8.2.2 initializes the HTTP administration server with a hardcoded default password. In repeater/webgui/settings.c:197, when settings2.txt is absent on first run the repeate...
How severe is CVE-2026-7839?
CVE-2026-7839 has been rated CRITICAL with a CVSS base score of 9.1/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-7839?
Check the references section above for vendor advisories and patch information. Affected products include: Uvnc Ultravnc.