CVE-2026-7839 json
UltraVNC repeater ships hardcoded default admin password allowing unauthenticated admin access
published 2026-07-01 4 mo ago modified 2026-10-25 14 d ago also EUVD-2026-40885
- cvss
- 9.1
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.7%
- EPSS 0.7% chance of exploitation in 30 days, percentile 51%
- public exploits
- 0
- none known
Summary
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.
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- total
- Assessed
- 4 mo ago
Exploit prediction
0.66% chance of exploitation in the next 30 days, higher than 51% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 9.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
Affected products
- uvnc UltraVNC
Classification
- Weakness
-
- CWE-798 Use of Hard-coded Credentials
References
-
uvnc.com
/
vendor-advisory, product, release-notes
-
github.com
/ultravnc/UltraVNC
product
- securin.io /zero-days/cve-2026-7839-hardcoded-default-admin-password-adminadmi2-ultravnc-repeater
Sources
- CVE List CVE-2026-7839
- NVD CVE-2026-7839
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