CVE-2026-92761 in WebVirtCloud
Summary
by MITRE • 09/16/2026
WebVirtCloud fails to properly validate permission flags in UserInstance grants, allowing view-only users to perform privileged actions. Attackers with read-only grants can power off virtual machines, reset root passwords, install SSH keys, and manage ISO images by exploiting the get_instance gate that only checks grant existence.
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Analysis
by VulDB Data Team • 09/16/2026
The vulnerability identified in WebVirtCloud represents a critical failure in access control logic within its instance management subsystem. Specifically, the flaw resides in how permission flags are validated during UserInstance grants. The system relies on an authentication mechanism known as get_instance to determine whether a user has sufficient privileges to perform actions against a virtual machine instance. However, this gate performs only a binary check for the existence of any grant rather than evaluating the specific type or scope of permissions associated with that grant. This architectural oversight means that users assigned read-only or view-only roles are inadvertently granted administrative capabilities because the system fails to distinguish between different levels of access rights when processing requests.
From a technical perspective, this is a classic example of broken object level authorization where the application logic does not enforce granular permissions on individual resources. The get_instance function acts as an entry point for various management operations but lacks the necessary conditional checks to ensure that only users with appropriate write or administrative privileges can execute these functions. By bypassing the intended permission hierarchy, attackers who possess minimal access rights can interact with sensitive backend APIs and trigger state-changing operations that should be restricted to system administrators or power users. This misconfiguration effectively nullifies the security boundary established by role-based access control policies within the virtualization management platform.
The operational impact of this vulnerability is severe due to the high-privilege nature of the actions it enables. An attacker with read-only access can compromise the availability, integrity, and confidentiality of hosted workloads. They are capable of powering off critical virtual machines, which leads directly to service disruption and potential data loss if unsaved states are lost during shutdown. Furthermore, by resetting root passwords or installing SSH keys, an adversary gains persistent unauthorized administrative control over the guest operating systems. This allows for complete system compromise, lateral movement within the network, and exfiltration of sensitive data stored on those instances. Additionally, the ability to manage ISO images could allow attackers to mount malicious boot media or replace legitimate installation sources, further expanding their attack surface.
This vulnerability aligns with CWE-269 Improper Privilege Management as it involves a failure to enforce proper authorization levels for system functions. It also maps closely to MITRE ATT&CK techniques such as T1078 Valid Accounts and T1543 Create or Modify System Process, since the attacker leverages legitimate but misconfigured credentials to perform administrative tasks. The exploitation path typically involves identifying valid user accounts with view-only access and then crafting requests that target instance management endpoints without providing evidence of higher-level permissions.
Mitigation strategies must focus on hardening the authorization logic within the WebVirtCloud application code. Developers should modify the get_instance gate to explicitly check for specific permission flags rather than merely verifying grant existence. Implementing strict role-based access control checks at every privileged endpoint is essential to ensure that only users with designated administrative or write privileges can execute actions like power management, password resets, and SSH key manipulation. Additionally, conducting a comprehensive audit of all API endpoints to verify they adhere to the principle of least privilege will help prevent similar bypasses in other modules. Regular security testing including penetration tests focused on access control flaws is recommended to identify and remediate such logic errors before they can be exploited in production environments.