CVE-2026-7839

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 v3 9.1 CRITICAL

9.1^/10

CVSS v3 : CRITICAL

Vector :

Exploitability : 3.9 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/ultravnc/UltraVNC	Product
https://uvnc.com/	Product Release Notes
https://www.securin.io/zero-days/cve-2026-7839-hardcoded-default-admin-password-adminadmi2-ultravnc-repeater

Configurations

Configuration 1 (hide)

cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:*

History

09 Jul 2026, 06:16

Type	Values Removed	Values Added
References		() https://www.securin.io/zero-days/cve-2026-7839-hardcoded-default-admin-password-adminadmi2-ultravnc-repeater -

02 Jul 2026, 15:30

Type	Values Removed	Values Added
CPE		cpe:2.3:a:uvnc:ultravnc::::::::
First Time		Uvnc Uvnc ultravnc
References	~~() https://github.com/ultravnc/UltraVNC -~~	() https://github.com/ultravnc/UltraVNC - Product
References	~~() https://uvnc.com/ -~~	() https://uvnc.com/ - Product, Release Notes

01 Jul 2026, 05:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-07-01 05:16

Updated : 2026-07-09 06:16

NVD link : CVE-2026-7839

Mitre link : CVE-2026-7839

CVE.ORG link : CVE-2026-7839

JSON object : View

Products Affected

uvnc

ultravnc

CWE

CWE-798

Use of Hard-coded Credentials

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