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🛡️ CVE-2026-7839 — ultravnc

🔴 CVSS 9.1 — Critical ✅ No Known Exploit CWE-798 NVD
9.1
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: High — total loss, or loss the attacker controls.
  • Availability impact: None.

Weakness class

CVE-2026-7839 is classified as CWE-798: Use of Hard-coded Credentials. Credentials are built into the product, so they are identical on every installation and cannot be rotated.

Affected software

CVE-2026-7839 is recorded against 1 package.

  • ultravnc (fixed in 1.8.2.2)

Timeline and source

Published on 1 July 2026 and last revised on 9 July 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com
uvnc.com
www.securin.io

Other advisories for this package

ultravnc has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-798: Use of Hard-coded Credentials) in other software:

Details

Severity CRITICAL
CVSS Score 9.1
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CWE CWE-798
Public Exploit ✅ No
Source NVD
Published 2026-07-01
Updated 2026-08-20
Modified 2026-07-09
Fix URL N/A

Affected Packages

Software From version Fixed in
ultravnc — 1.8.2.2

Similar Threats

Exploit Protection

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CVE-2026-7839 carries CVSS 9.1 Critical rating. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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