CVE-2026-90450 in Malcolm
Summary
by MITRE • 09/12/2026
The application's role-authorization lookup defaults to granting access when a request handler's name is not present in its table of role requirements, rather than defaulting to deny. Any request handler that is not explicitly registered in this table is reachable by any authenticated user regardless of their assigned role, and any newly added handler is fail-open by default until explicitly added to the table.
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Analysis
by VulDB Data Team • 09/12/2026
The described vulnerability represents a critical failure in access control logic, specifically categorized under CWE-284 Improper Access Control or more precisely CWE-732 Incorrect Permission Assignment for Critical Resource when viewed through the lens of privilege escalation risks. The core technical flaw lies in the application's authorization mechanism defaulting to an allow state rather than a deny state when processing role-authorization lookups. In secure software design, particularly within frameworks that utilize handler-based routing or endpoint mapping, it is standard practice to implement a fail-safe principle where any request not explicitly permitted by policy is automatically denied. By reversing this logic and granting access by default for unregistered handlers, the application creates a significant security gap that undermines the integrity of its authentication and authorization systems.
This architectural decision results in a scenario where authenticated users can bypass intended role-based restrictions simply by interacting with endpoints or request handlers that have not been explicitly defined in the administrative configuration table. Since newly added handlers are fail-open by default, any developer who introduces new functionality without immediately updating the security policy effectively exposes those features to all authenticated accounts regardless of their assigned privileges. This creates a dynamic where the scope of accessible resources expands uncontrollably as the application evolves, leading to potential unauthorized access to sensitive data or administrative functions that were never intended for general user consumption.
From an operational impact perspective, this vulnerability allows attackers who have obtained valid credentials through phishing, credential stuffing, or other means to escalate their privileges indirectly by accessing restricted endpoints. If a high-privilege handler is added but not yet registered in the role table, any low-level authenticated user can execute commands associated with that handler. This effectively nullifies the distinction between different user roles and can lead to data exfiltration, modification of critical system configurations, or complete compromise of the application's backend services depending on the capabilities exposed by these unregistered handlers.
To mitigate this vulnerability, developers must immediately refactor the authorization middleware to enforce a default-deny policy. This involves ensuring that any request handler not explicitly listed in the role-requirement table is rejected with an appropriate HTTP error code such as 403 Forbidden or 401 Unauthorized depending on authentication status. Additionally, automated testing and static analysis tools should be configured to flag new endpoints during the development lifecycle if they are not accompanied by corresponding authorization rules. Implementing a comprehensive access control list that requires explicit permission grants for every endpoint will ensure that security policies remain tightly coupled with application functionality, preventing future instances of this fail-open behavior from compromising system integrity. This approach aligns with industry best practices outlined in OWASP guidelines regarding insecure direct object references and broken access control, ensuring that the principle of least privilege is strictly enforced across all application components.