PT-2026-54489 · Uvnc · Ultravnc

Published 2026-07-01 · Updated 2026-07-01 · CVE-2026-7839

Mitre

CVSS v3.1

9.1

Critical

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

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.

Fix

Using Hardcoded Credentials

Weakness Enumeration

CWE-798

Related Identifiers

CVE-2026-7839

Affected Products

Ultravnc

References · 3

• https://nvd.nist.gov/vuln/detail/CVE-2026-7839 · Security Note
• https://uvnc.com · Vendor Advisory
• https://github.com/ultravnc/UltraVNC · Note