CVE-2020-11561 in Express Invoice
Summary
by MITRE
In NCH Express Invoice 7.25, an authenticated low-privilege user can enter a crafted URL to access higher-privileged functionalities such as the "Add New Item" screen.
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Analysis
by VulDB Data Team • 05/17/2024
The vulnerability identified as CVE-2020-11561 represents a critical authorization bypass flaw within NCH Express Invoice version 7.25 that allows authenticated users with limited privileges to escalate their access rights through manipulation of URL parameters. This issue stems from inadequate input validation and improper access control mechanisms within the application's web interface, creating a pathway for privilege escalation that directly violates fundamental security principles of least privilege and principle of least privilege enforcement. The vulnerability specifically affects the application's session management and role-based access control implementation, where the system fails to properly verify user permissions before granting access to restricted functionality.
The technical exploitation of this vulnerability occurs through the manipulation of Uniform Resource Identifiers that typically contain parameters controlling access to specific application modules. When an authenticated user with lower privileges constructs a specially crafted URL containing specific parameters or path components, the application's authorization checks are bypassed, allowing access to administrative functions such as the "Add New Item" screen. This flaw demonstrates a classic case of insufficient authorization validation where the system relies on client-side URL construction rather than server-side verification of user permissions. The vulnerability's impact is particularly concerning as it enables users to access functionality that should only be available to administrators or users with elevated privileges, potentially leading to data manipulation, unauthorized modifications, and privilege abuse within the invoicing system.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it creates potential pathways for data integrity compromise and system-wide security degradation. An attacker with access to any valid user account can leverage this vulnerability to gain access to sensitive administrative functions without proper authorization, potentially leading to unauthorized modifications of invoice templates, user management, system configurations, and financial data manipulation. This authorization bypass represents a significant weakening of the application's security model and violates multiple security standards including those outlined in the OWASP Top Ten 2017, specifically addressing broken access control vulnerabilities. The vulnerability also aligns with ATT&CK technique T1078 which covers valid accounts and privilege escalation, as it allows an attacker to leverage legitimate user credentials to access elevated functionality.
Mitigation strategies for this vulnerability require immediate implementation of comprehensive access control measures including server-side validation of all URL parameters and strict enforcement of role-based access controls. Organizations should implement proper input sanitization and validation to prevent parameter manipulation, establish robust session management protocols, and ensure that all access control decisions are made server-side rather than relying on client-side URL construction. The fix should include implementing a centralized authorization service that validates user permissions for each request, implementing proper logging and monitoring of access attempts, and ensuring that all administrative functions require explicit verification of elevated privileges before execution. Additionally, regular security assessments and code reviews should be conducted to identify similar authorization bypass vulnerabilities within the application's architecture, following security best practices established in NIST SP 800-53 and ISO/IEC 27001 frameworks to prevent similar issues from occurring in future releases.