# CVE-2026-7839: UltraVNC Repeater hardcoded password in HTTP administration server

Source: https://junglewise.ai/threats/cve-2026-7839-ultravnc-repeater-hardcoded-password-in-http-administration-server  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-01. Updated: 2026-07-01  
License: CC BY 4.0 with a link back

CVE-2026-7839 · Severity: critical · CVSS 9.1 · Published 2026-07-01

UltraVNC Repeater, a tool used to facilitate remote desktop connections through firewalls, contains a hardcoded administrative password. On new or unmodified installations, an attacker can use this well-known password to log into the web management interface. This allows unauthorized individuals to view active remote support sessions and change security rules, potentially leading to unauthorized access to internal systems.

Technologies: [UltraVNC Repeater](https://junglewise.ai/threats/technologies/repeater). Vendors: [UltraVNC](https://junglewise.ai/threats/vendors/ultravnc).

## Quick answers

**Is CVE-2026-7839 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-7839 being exploited in the wild.

**How severe is CVE-2026-7839?** Critical severity, with a CVSS score of 9.1, published 1 July 2026.

**Which products and versions are affected?** UltraVNC Repeater through 1.8.2.2.

**Is there a fix for CVE-2026-7839?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-7839 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-7839?** Check whether you run UltraVNC Repeater at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

UltraVNC Repeater through 1.8.2.2 contains a hardcoded credential vulnerability (CWE-798) in its HTTP administration interface. In `repeater/webgui/settings.c`, the application initializes the admin password to the literal string "adminadmi2" if the configuration file `settings2.txt` is missing. The HTTP Basic-auth handler, `wi_decode_auth()`, validates this password without implementing rate-limiting or account lockout mechanisms. A remote attacker can exploit this by accessing the repeater's HTTP port (default TCP 80) and authenticating with the default credentials. Successful exploitation grants full administrative access, including the ability to modify allow/deny rules and monitor active sessions. Version 1.8.2.4 appears to be available as a potential update.

## Affected products

- UltraVNC UltraVNC Repeater through 1.8.2.2

## Timeline

- 2026-07-01: advisory: CVE-2026-7839 published by NVD

## References

- [https://github.com/ultravnc/UltraVNC](https://github.com/ultravnc/UltraVNC)
- [https://uvnc.com/](https://uvnc.com/)

## Related threats

- [UltraVNC Repeater out-of-bounds write in allow/deny rule parser](https://junglewise.ai/threats/cve-2026-7829-ultravnc-repeater-out-of-bounds-write-in-allow-deny-rule-parser)
- [UltraVNC Repeater integer overflow in HTTP request logging](https://junglewise.ai/threats/cve-2026-7828-ultravnc-repeater-integer-overflow-in-http-request-logging)
- [UltraVNC Repeater off-by-one error in HTTP Basic authentication](https://junglewise.ai/threats/cve-2026-44042-ultravnc-repeater-off-by-one-error-in-http-basic-authentication)