CVE-2026-7839
UltraVNC repeater ships hardcoded default admin password allowing unauthenticated admin access
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.
INFO
Published Date :
July 1, 2026, 5:16 a.m.
Last Modified :
July 9, 2026, 6:16 a.m.
Remotely Exploit :
Yes !
Source :
33c584b5-0579-4c06-b2a0-8d8329fcab9c
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | CRITICAL | 33c584b5-0579-4c06-b2a0-8d8329fcab9c |
Solution
- Change the default password from 'adminadmi2' immediately.
- Secure the administration interface with strong credentials.
- Ensure no default passwords remain after configuration.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-7839.
| URL | 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 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-7839 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-7839
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-7839 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-7839 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by 33c584b5-0579-4c06-b2a0-8d8329fcab9c
Jul. 09, 2026
Action Type Old Value New Value Added Reference https://www.securin.io/zero-days/cve-2026-7839-hardcoded-default-admin-password-adminadmi2-ultravnc-repeater -
Initial Analysis by [email protected]
Jul. 02, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:* versions up to (including) 1.8.2.2 Added Reference Type securin: https://github.com/ultravnc/UltraVNC Types: Product Added Reference Type securin: https://uvnc.com/ Types: Product, Release Notes -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 01, 2026
Action Type Old Value New Value Added SSVC {'id': 'CVE-2026-7839', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'none'}, {'automatable': 'yes'}, {'technicalImpact': 'total'}], 'version': '2.0.3', 'timestamp': '2026-07-01T12:32:28.823292Z'} -
New CVE Received by 33c584b5-0579-4c06-b2a0-8d8329fcab9c
Jul. 01, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'uvnc', 'modules': ['repeater'], 'product': 'UltraVNC', 'versions': [{'status': 'affected', 'version': '0', 'versionType': 'custom', 'lessThanOrEqual': '1.8.2.2'}], 'defaultStatus': 'unaffected'}] Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Added CWE CWE-798 Added Reference https://github.com/ultravnc/UltraVNC Added Reference https://uvnc.com/