A Vulnerability in WHM cPanel and WP Squared Could Allow for Remote Code Execution

A vulnerability has been discovered in WHM, cPanel, and WP Squared that could allow for remote code execution. WHM, cPanel, and WP Squared are Linux-based web hosting control panels for server and website management. While WHM provides server-level control, cPanel provides administrator access to the website backend, webmail, and databases. Successful exploitation could allow unauthenticated remote attackers to bypass authentication and gain unauthorized administrative access to the affected systems, ultimately leading to remote code execution. 

Threat actors are actively exploiting CVE-2026-41940 and the vulnerability was added to CISA’s Known Exploited Vulnerabilities (KEV) Catalog. Additionally, watchTowr Labs published a detailed technical analysis of the vulnerability and proof of concept exploitation code against internet-exposed cPanel or WebHost Manager (WHM). The entire exploit chain requires only a small number of HTTP requests and no valid credentials, after which full WHM API access provides root-level remote code execution through legitimate WHM-exposed features. According to KnownHost CEO, Daniel Pearson, threat actors began exploiting this vulnerability as early as February 23, 2026, approximately two months before cPanel issued its emergency patch on April 28, 2026. Following public disclosure, exploitation has escalated, with threat actors compromising servers and deploying a Go-based Linux encryptor associated with the “Sorry” ransomware campaign. Shadowserver reported that 44,000 IP addresses were associated with active scanning and exploit activity of cPanel instances. There is a variety of other post-compromise activity, including Mirai botnet installation, credential harvesting, and cyber espionage operations targeting government and military entities in Southeast Asia.

A vulnerability has been discovered in WHM, cPanel, and WP Squared that could allow for remote code execution. Details of the vulnerability are as follows:

Tactic: Initial Access (TA0001):

Technique: Exploit Public-Facing Application (T1190):

• cPanel and WHM versions after 11.40 contain an authentication bypass vulnerability in the login flow that allows unauthenticated remote attackers to gain unauthorized access to the control panel. (CVE-2026-41940).

Successful exploitation could allow unauthenticated remote attackers to bypass authentication and gain unauthorized administrative access to the affected systems, ultimately leading to remote code execution.

We recommend the following actions be taken: 

• Apply appropriate updates provided by WHM, cPanel, and WP Squared or other vendors which use this software to vulnerable systems immediately after appropriate testing. (M1051: Update Software)
• Safeguard 7.1 : Establish and Maintain a Vulnerability Management Process: Establish and maintain a documented vulnerability management process for enterprise assets. Review and update documentation annually, or when significant enterprise changes occur that could impact this Safeguard.
• Safeguard 7.2: Establish and Maintain a Remediation Process: Establish and maintain a risk-based remediation strategy documented in a remediation process, with monthly, or more frequent, reviews.
• Safeguard 7.4: Perform Automated Application Patch Management: Perform application updates on enterprise assets through automated patch management on a monthly, or more frequent, basis.
• Safeguard 7.5 : Perform Automated Vulnerability Scans of Internal Enterprise Assets: Perform automated vulnerability scans of internal enterprise assets on a quarterly, or more frequent, basis. Conduct both authenticated and unauthenticated scans, using a SCAP-compliant vulnerability scanning tool.
• Safeguard 7.7: Remediate Detected Vulnerabilities: Remediate detected vulnerabilities in software through processes and tooling on a monthly, or more frequent, basis, based on the remediation process.
• Safeguard 12.1: Ensure Network Infrastructure is Up-to-Date: Ensure network infrastructure is kept up-to-date. Example implementations include running the latest stable release of software and/or using currently supported network-as-a-service (NaaS) offerings. Review software versions monthly, or more frequently, to verify software support.
• Safeguard 18.1: Establish and Maintain a Penetration Testing Program: Establish and maintain a penetration testing program appropriate to the size, complexity, and maturity of the enterprise. Penetration testing program characteristics include scope, such as network, web application, Application Programming Interface (API), hosted services, and physical premise controls; frequency; limitations, such as acceptable hours, and excluded attack types; point of contact information; remediation, such as how findings will be routed internally; and retrospective requirements.
• Safeguard 18.2: Perform Periodic External Penetration Tests: Perform periodic external penetration tests based on program requirements, no less than annually. External penetration testing must include enterprise and environmental reconnaissance to detect exploitable information. Penetration testing requires specialized skills and experience and must be conducted through a qualified party. The testing may be clear box or opaque box.
• Safeguard 18.3: Remediate Penetration Test Findings: Remediate penetration test findings based on the enterprise’s policy for remediation scope and prioritization.
• Apply the Principle of Least Privilege to all systems and services. Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack. (M1026: Privileged Account Management)
• Safeguard 4.7: Manage Default Accounts on Enterprise Assets and Software: Manage default accounts on enterprise assets and software, such as root, administrator, and other pre-configured vendor accounts. Example implementations can include: disabling default accounts or making them unusable.
• Safeguard 5.5: Establish and Maintain an Inventory of Service Accounts: Establish and maintain an inventory of service accounts. The inventory, at a minimum, must contain department owner, review date, and purpose. Perform service account reviews to validate that all active accounts are authorized, on a recurring schedule at a minimum quarterly, or more frequently.
• Vulnerability scanning is used to find potentially exploitable software vulnerabilities to remediate them. (M1016: Vulnerability Scanning)
• Safeguard 16.13: Conduct Application Penetration Testing: Conduct application penetration testing. For critical applications, authenticated penetration testing is better suited to finding business logic vulnerabilities than code scanning and automated security testing. Penetration testing relies on the skill of the tester to manually manipulate an application as an authenticated and unauthenticated user.
• Architect sections of the network to isolate critical systems, functions, or resources. Use physical and logical segmentation to prevent access to potentially sensitive systems and information. Use a DMZ to contain any internet-facing services that should not be exposed from the internal network. Configure separate virtual private cloud (VPC) instances to isolate critical cloud systems. (M1030: Network Segmentation)
• Safeguard 12.2: Establish and Maintain a Secure Network Architecture: Establish and maintain a secure network architecture. A secure network architecture must address segmentation, least privilege, and availability, at a minimum.
• Use capabilities to detect and block conditions that may lead to or be indicative of a software exploit occurring. (M1050: Exploit Protection)
• Safeguard 10.5: Enable Anti-Exploitation Features: Enable anti-exploitation features on enterprise assets and software, where possible, such as Microsoft? Data Execution Prevention (DEP), Windows? Defender Exploit Guard (WDEG), or Apple? System Integrity Protection (SIP) and Gatekeeper™.