CVE-2026-7839 | UltraVNC repeater ships hardcoded default admin password allowing unauthenticated admin access

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: 2026-07-01 Last update: 2026-07-09 Assigner: 33c584b5-0579-4c06-b2a0-8d8329fcab9c Source: 33c584b5-0579-4c06-b2a0-8d8329fcab9c
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-7839 is rated Moderate Risk (46.8/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.37%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-7839

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-07-09 0.33% 0.37% +0.05%
2 2026-07-01 — 0.33% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-7839

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.1 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 5.2 33c584b5-0579-4c06-b2a0-8d8329fcab9c

Weakness enumeration for CVE-2026-7839

GitHub Security Advisory for CVE-2026-7839

GHSA-h7cc-6wq3-9h7x · Severity: critical — UltraVNC repeater through 1.8.2.2 initializes the HTTP administration server with a hardcoded...

Affected software / configurations for CVE-2026-7839

Vendor Product Version Raw CPE
uvnc ultravnc <= 1.8.2.2 cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:*

References for CVE-2026-7839

cvelogic Threat Intelligence