9.1

CVE-2026-7839: uvnc ultravnc Use of Hard-coded Credentials

CVSS: 9.1v3.1CriticalModified
Published 01-07-2026Last modified 09-07-2026
Open JSON

Vulnerability summary

CVE-2026-7839 is a critical (CVSS 9.1) Use of Hard-coded Credentials vulnerability in uvnc ultravnc. EPSS estimates a 0.66% chance of exploitation in the next 30 days, higher than 50.4% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.1/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.66%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 01-07-2026
    PublishedVulnerability first disclosed.
  2. 09-07-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.66%

Chance of exploitation in the next 30 days

Percentile

50%

Versus all other CVEs

30-day change

0.00 pp

From 0.66% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.66%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Uvnc1 product

1 vendor · 1 product

References

3 links