CVE-2016-20004 in REST-JSON Project
Summary
by MITRE • 01/01/2021
The REST/JSON project 7.x-1.x for Drupal allows field access bypass, aka SA-CONTRIB-2016-033. NOTE: This project is not covered by Drupal's security advisory policy.
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Analysis
by VulDB Data Team • 08/17/2026
The vulnerability identified as SA-CONTRIB-2016-033 represents a critical authorization flaw within the REST/JSON module for Drupal version 7.x, specifically affecting development branches such as 7.x-1.x. This issue stems from an improper implementation of access control mechanisms when handling field-level permissions through the JSON API interface. In standard web application architectures, particularly those built on content management systems like Drupal, security relies heavily on the principle of least privilege and strict enforcement of user roles against specific resource attributes. The REST/JSON module facilitates data exchange by exposing entity fields via HTTP endpoints, but in this instance, the logic governing who can read or write to these fields fails to correctly validate the requesting user's permissions against the field definitions before processing the request. This architectural oversight allows an authenticated attacker with lower-level privileges to bypass intended restrictions and access sensitive data associated with restricted fields that should otherwise be invisible or immutable to their account level.
From a technical perspective, this flaw is classified under CWE-284, which denotes Improper Access Control, specifically manifesting as a failure to enforce proper authorization checks on specific resources within an application layer API. The vulnerability exploits the gap between general entity access and granular field-level security policies. When a user submits a request via the REST interface, the system retrieves the requested data but neglects to cross-reference the fields being accessed against the current session's permission set defined by Drupal's core field permissions module or custom role configurations. Consequently, the application returns full object representations including protected fields rather than filtering them out based on the requester's identity and assigned roles. This behavior effectively neutralizes the security boundaries established at the content management layer, rendering those controls ineffective when accessed through the API vector.
The operational impact of this vulnerability is significant for organizations relying on Drupal to manage sensitive information such as personally identifiable information (PII), financial records, or proprietary business data. An attacker can leverage this flaw to perform unauthorized data exfiltration by querying endpoints and retrieving field values that are not supposed to be visible in the user interface or standard API responses. This leads directly to a compromise of confidentiality integrity within the application's security posture. Furthermore, depending on the specific fields exposed and whether write operations were also affected by similar logic gaps, there could be implications for data integrity if attackers can modify restricted attributes. The lack of proper access control means that internal business rules regarding data visibility are bypassed without requiring elevated privileges or complex exploitation techniques beyond standard API interaction capabilities.
In terms of threat modeling and industry frameworks, this vulnerability aligns with the MITRE ATT&CK technique T1078, Valid Accounts, as it allows an attacker to use legitimate credentials to access resources they should not have permission to view. It also relates to T1530, Data from Cloud Storage Objects, if the exposed fields contain data stored in external systems or databases linked through Drupal entities. The attack vector is primarily remote and requires authentication, placing it within the scope of authenticated API abuse rather than unauthenticated injection attacks. This distinction highlights that even secure login mechanisms are insufficient if the underlying resource authorization logic is flawed at the application layer.
Mitigation strategies for this vulnerability require immediate attention to both software updates and architectural reviews. Since Drupal's official security advisory policy explicitly excludes contributions from projects like REST/JSON, users must rely on maintaining their contributed modules through direct vendor or community channels rather than core update mechanisms. Administrators should upgrade to a patched version of the module where field access checks have been properly integrated into the JSON serialization process. Until an updated package is available, temporary mitigations include disabling the affected endpoints if they are not strictly necessary for business operations, implementing strict IP whitelisting on API gateways to limit exposure, and deploying Web Application Firewalls configured with rules that detect anomalous field access patterns indicative of enumeration attacks. Additionally, organizations should conduct a thorough audit of their Drupal modules to identify other contributed projects that may suffer from similar authorization bypass flaws, ensuring that all third-party integrations adhere to rigorous security standards consistent with CWE-284 remediation guidelines.