CVE-2026-42376 Vulnerability Analysis & Exploit Details

CVE-2026-42376
Vulnerability Scoring

9.8
/10
Critical Risk

As a catastrophic security flaw, CVE-2026-42376 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-2026-42376 Details

Status: Received on 04 May 2026, 17:16 UTC

Published on: 04 May 2026, 17:16 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:H

CVE-2026-42376 Vulnerability Summary

CVE-2026-42376: D-Link DIR-456U Hardware Revision A1 (End-of-Life, EOL) contains a hardcoded telnet backdoor. The device starts a telnet daemon at boot via /etc/init0.d/S80telnetd.sh with the username "Alphanetworks" and the static password "whdrv01_dlob_dir456U" read from /etc/config/image_sign. The custom telnetd binary accepts a -u user:password flag, and the custom login binary uses strcmp() to validate credentials. Successful authentication grants an unauthenticated attacker on the local network a root shell with full administrative control. The device has reached End-of-Life (EOL) and will not receive patches.

Assessing the Risk of CVE-2026-42376

Access Complexity Graph

The exploitability of CVE-2026-42376 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-2026-42376

With low attack complexity and no required privileges, CVE-2026-42376 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-2026-42376, 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-2026-42376, 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-2026-42376 can result in unauthorized access to sensitive data, severely compromising data privacy.
  • Integrity: High
    CVE-2026-42376 could allow unauthorized modifications to data, potentially affecting system reliability and trust.
  • Availability: High
    CVE-2026-42376 can disrupt system operations, potentially causing complete denial of service (DoS).

CVE-2026-42376 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.

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