CVE-2026-7839 Details
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.
A vulnerability exists in UltraVNC Repeater versions through 1.8.2.2, where the HTTP administration server is initialized with a hardcoded default password. On the first run, if the settings2.txt file is missing, the repeater writes 'adminadmi2' as the admin password. The HTTP Basic-auth handler checks this password without any rate limiting or lockout. This flaw allows remote attackers who can access the repeater's HTTP port (default TCP 80) to authenticate as administrators using the default credential, thereby gaining full control over the repeater's configuration, including allow/deny rules and session visibility.
Users can update to UltraVNC Repeater version 1.8.2.4 or later, where this vulnerability has been addressed.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jul 1, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/ultravnc/UltraVNC | securin | Product |
| https://uvnc.com/ | securin | ProductRelease Notes |
| https://www.securin.io/zero-days/cve-2026-7839-hardcoded-default-admin-password-adminadmi2-ultravnc-repeater | securin |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-798 | Use of Hard-coded Credentials | securin |
Affected Products
| Product | Versions |
|---|---|
| uvnc ultravnc | <= 1.8.2.2 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 9, 2026 | CVE Modified | securin |
| Jul 2, 2026 | Initial Analysis | [email protected] |
| Jul 1, 2026 | CVE Modified | CISA-ADP |
| Jul 1, 2026 | New CVE Received | securin |