CVE-2026-7839 Vulnerability Analysis & Exploit Details

CVE-2026-7839
Vulnerability Scoring

9.1
/10
Critical Risk

As a catastrophic security flaw, CVE-2026-7839 has severe implications, demanding immediate intervention.

Attack Complexity Details

  • Attack Complexity: Low
    Exploits can be performed without significant complexity or special conditions.
  • Attack Vector: Network
    Vulnerability is exploitable over a network without physical access.
  • Privileges Required: None
    No privileges are required for exploitation.
  • Scope: Unchanged
    Exploit remains within the originally vulnerable component.
  • User Interaction: None
    No user interaction is necessary for exploitation.

CVE-2026-7839 Details

Status: Received on 01 Jul 2026, 05:16 UTC

Published on: 01 Jul 2026, 05:16 UTC

CVSS Release: version 3

CVSS3 Source

33c584b5-0579-4c06-b2a0-8d8329fcab9c

CVSS3 Type

Secondary

CVSS3 Vector

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

CVE-2026-7839 Vulnerability Summary

CVE-2026-7839: 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.

Assessing the Risk of CVE-2026-7839

Access Complexity Graph

The exploitability of CVE-2026-7839 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2026-7839

With low attack complexity and no required privileges, CVE-2026-7839 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2026-7839, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2026-7839, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: High
    Exploiting CVE-2026-7839 can result in unauthorized access to sensitive data, severely compromising data privacy.
  • Integrity: High
    CVE-2026-7839 could allow unauthorized modifications to data, potentially affecting system reliability and trust.
  • Availability: None
    CVE-2026-7839 does not impact system availability.

CVE-2026-7839 References

External References

CWE Common Weakness Enumeration

CWE-798

CAPEC Common Attack Pattern Enumeration and Classification

  • Read Sensitive Constants Within an Executable CAPEC-191 An adversary engages in activities to discover any sensitive constants present within the compiled code of an executable. These constants may include literal ASCII strings within the file itself, or possibly strings hard-coded into particular routines that can be revealed by code refactoring methods including static and dynamic analysis.
  • Try Common or Default Usernames and Passwords CAPEC-70 An adversary may try certain common or default usernames and passwords to gain access into the system and perform unauthorized actions. An adversary may try an intelligent brute force using empty passwords, known vendor default credentials, as well as a dictionary of common usernames and passwords. Many vendor products come preconfigured with default (and thus well-known) usernames and passwords that should be deleted prior to usage in a production environment. It is a common mistake to forget to remove these default login credentials. Another problem is that users would pick very simple (common) passwords (e.g. "secret" or "password") that make it easier for the attacker to gain access to the system compared to using a brute force attack or even a dictionary attack using a full dictionary.

Protect Your Infrastructure against CVE-2026-7839: Combat Critical CVE Threats

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