CVE-2026-107333 in Malcolm
Summary
by MITRE • 10/08/2026
Malcolm's nginx based reverse proxy contains a URL path normalization inconsistency between its Lua based role-based access control (RBAC) authorization layer and nginx's own request routing logic. An authenticated user can craft a specially formatted request path to bypass role-based restrictions and reach administrative or role gated endpoints they should not have access to. This affects all restricted paths protected by the RBAC authorization layer, including file upload, PHP server, htadmin, and authentication management interfaces.
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Analysis
by VulDB Data Team • 10/08/2026
The vulnerability described involves a critical security flaw in Malcolm's nginx-based reverse proxy architecture, specifically stemming from an inconsistency between URL path normalization mechanisms employed by different layers of the system. This application serves as a central hub for managing network traffic analysis data, relying heavily on role-based access control to restrict sensitive administrative functions such as file uploads, PHP server interactions, and authentication management interfaces. The core issue arises because the Lua-based authorization layer responsible for enforcing RBAC policies processes incoming requests differently than the underlying nginx web server handles request routing. This discrepancy creates a path traversal or normalization bypass opportunity that allows authenticated users with lower privileges to escalate their access rights inadvertently through crafted HTTP requests.
From a technical perspective, URL path normalization is essential for ensuring that different representations of the same resource are treated consistently by security controls and application logic. In this scenario, an attacker can manipulate the request URI using specific encoding techniques or structural anomalies in the path string. While the Lua RBAC module interprets one version of the path to determine if the user has permission to access a restricted endpoint, nginx routes the actual request based on its own parsing rules which may interpret the same malformed path as pointing to an unprotected resource or bypassing the authorization check entirely. This separation of concerns between authentication enforcement and request routing is a common architectural pitfall when integrating custom scripting layers with robust web servers like nginx. The lack of synchronized normalization logic means that security decisions made in the Lua layer can be effectively nullified by the transport-layer handling performed by nginx, leading to an unauthorized access condition.
The operational impact of this vulnerability is severe given the nature of the affected endpoints. Since the flaw impacts all restricted paths protected by the RBAC authorization layer, it compromises the integrity of administrative functions including file upload capabilities and authentication management interfaces. An authenticated user with standard privileges could potentially execute arbitrary code via PHP server interactions, modify system configurations through htadmin, or exfiltrate sensitive data through unrestricted file uploads. This effectively undermines the principle of least privilege within the application, allowing lateral movement within the system if combined with other vulnerabilities. The ability to bypass role-based restrictions means that any user account, regardless of its assigned security clearance level, can interact with administrative tools intended only for high-privilege administrators, thereby exposing the entire infrastructure to potential compromise or disruption.
This vulnerability aligns closely with CWE-284 Improper Access Control and CWE-697 Incorrect Comparison, as it involves a failure in enforcing access restrictions due to inconsistent handling of input data across different system components. In terms of offensive security frameworks such as MITRE ATT&CK, this behavior is indicative of techniques related to Privilege Escalation via Bypassing Access Controls, where an actor exploits logical flaws rather than technical bugs in code execution or memory management. The attack vector typically involves crafting specific HTTP requests with manipulated URL paths that exploit the normalization gap, requiring only authenticated access which makes it particularly dangerous as it does not require initial unauthenticated exploitation to gain a foothold.
Mitigation strategies must focus on aligning the path interpretation logic between the Lua authorization layer and nginx routing engine. Developers should implement strict input validation and canonicalization of URL paths before any security checks are performed, ensuring that both layers see an identical representation of the requested resource. Utilizing standard libraries for URI normalization can help prevent discrepancies caused by encoding variations or structural ambiguities in request URIs. Additionally, implementing defense-in-depth measures such as verifying permissions at multiple points within the application stack and auditing all administrative endpoints for consistent access control enforcement is crucial. Regular security assessments focusing on logic flaws and integration issues between web server configurations and custom scripting layers will help identify similar inconsistencies before they can be exploited by malicious actors seeking to escalate privileges or bypass security controls.