CVE-2026-77140 in Telephone Directory Extension
Summary
by MITRE • 08/25/2026
The extension validates the HMAC of a frontend employee edit link only in the action that renders the edit form, not in the action that persists the change. An unauthenticated visitor who knows the UID of a visible employee record can send a direct POST request to the update action and overwrite that record without a valid edit link or any ownership check.
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Analysis
by VulDB Data Team • 08/25/2026
The described vulnerability represents a critical failure in access control logic within a web application, specifically categorized under CWE-284 Improper Access Control. The root cause lies in an asymmetric implementation of security checks where the integrity verification mechanism is applied inconsistently across different stages of the user interaction lifecycle. In this scenario, the system correctly validates the Hash-based Message Authentication Code (HMAC) associated with a frontend employee edit link when rendering the form for editing. This initial check ensures that only users possessing a valid, cryptographically signed token can view the editable interface. However, the security boundary is breached at the subsequent stage where the application processes the submitted data to persist changes to the database. The update action fails to re-validate the HMAC or perform any independent ownership verification against the authenticated session context, creating a significant gap in the defense-in-depth strategy.
This architectural flaw allows for an unauthenticated attacker who possesses knowledge of a visible employee record's unique identifier (UID) to bypass authentication and authorization controls entirely. By constructing a direct POST request to the update endpoint with arbitrary data associated with that UID, the attacker can overwrite sensitive information without ever having logged in or obtained a valid edit link. This type of attack is often referred to as an Insecure Direct Object Reference (IDOR), which falls under CWE-639. The absence of server-side validation for ownership means that any user who can guess or discover the UID structure of employee records can manipulate them, leading to potential data integrity issues and unauthorized modifications of critical business information.
The operational impact of this vulnerability is severe, as it compromises both confidentiality and integrity within the application's database. An attacker could alter sensitive personal details such as salaries, contact information, performance reviews, or internal notes associated with employees. Beyond immediate data corruption, this flaw can serve as a stepping stone for further attacks, including privilege escalation if the modified records influence role-based access controls, or social engineering campaigns using falsified employee data to deceive other staff members. The lack of audit trails specific to unauthorized modifications may also hinder incident response efforts, making it difficult to detect and attribute malicious activity promptly.
To mitigate this vulnerability, developers must enforce strict server-side authorization checks on all state-changing actions, not just those that render user interfaces. Specifically, the update action should validate that the current session's authenticated user owns the resource being modified or possesses explicit administrative privileges. This can be achieved by binding the HMAC validation to the specific HTTP method and ensuring it is checked during both form rendering and data persistence phases. Additionally implementing role-based access control (RBAC) policies that verify permissions before executing database updates will prevent unauthorized modifications. It is also recommended to use anti-CSRF tokens in conjunction with ownership checks to protect against cross-site request forgery attacks, which often exploit similar weaknesses in state-changing operations. Regular security code reviews and automated static analysis tools configured to detect improper access control patterns can help identify such logical flaws before deployment.