Home

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.

PUBLISHED Reserved 2026-05-05 | Published 2026-07-01 | Updated 2026-07-09 | Assigner securin




CRITICAL: 9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Problem types

Use of Hard-coded Credentials

Product status

Default status
unaffected

Any version
affected

Timeline

2026-06-02:Vulnerability discovered during security audit
2026-06-17:Reported to vendor (coordinated disclosure)
2026-09-15:Planned public disclosure (90-day window)

Credits

Arjun Basnet, Securin (arjun.basnet@securin.io) finder

References

uvnc.com/ (UltraVNC project page) vendor-advisory

github.com/ultravnc/UltraVNC (UltraVNC source repository) product

www.securin.io/...dmin-password-adminadmi2-ultravnc-repeater

cve.org (CVE-2026-7839)

nvd.nist.gov (CVE-2026-7839)

Download JSON