CVE-2016-20003 in REST-JSON Project
Summary
by MITRE • 01/01/2021
The REST/JSON project 7.x-1.x for Drupal allows user enumeration, 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 • 11/02/2026
The vulnerability identified as SA-CONTRIB-2016-033 affects the REST/JSON module for Drupal version 7.x, specifically within the 7.x-1.x development branch. It is critical to note that this project operates outside of Drupal's official security advisory policy, meaning it does not receive the same level of coordinated disclosure or immediate patching guarantees as core modules. The primary flaw in this implementation allows for user enumeration through RESTful API endpoints exposed by the module. This vulnerability stems from improper access controls and insufficient validation within the JSON-based web services provided by the module, enabling attackers to probe system responses and deduce valid usernames based on differences in error messages or response codes when querying non-existent versus existing user accounts.
From a technical perspective, this issue represents a classic case of information disclosure leading to account enumeration. When an attacker sends requests to specific REST endpoints with varying username parameters, the server's reaction differs depending on whether the user exists in the database. For instance, a request for an existing user might return a standard profile object or a different HTTP status code compared to a request for a non-existent user, which typically triggers a not found error or a distinct validation failure message. This side-channel information allows malicious actors to build a list of valid usernames on the target system without needing prior authentication credentials. The flaw is rooted in CWE-203, which describes observable discrepancy in behavior when an action succeeds versus fails, and aligns with MITRE ATT&CK technique T1087, specifically account discovery via local or remote queries.
The operational impact of this vulnerability extends beyond simple data leakage. By successfully enumerating valid usernames, attackers can significantly lower the barrier for subsequent attacks such as brute force password guessing, credential stuffing, or targeted phishing campaigns known as spear-phishing. Knowing which accounts are active allows adversaries to focus their efforts on high-value targets within an organization rather than wasting resources on inactive or non-existent accounts. This reconnaissance phase is often a precursor to more severe compromises, including unauthorized access and privilege escalation. Since the REST/JSON module facilitates programmatic interaction with Drupal content, compromising these endpoints can lead to further exploitation of other vulnerabilities if combined with additional flaws in the application logic or underlying CMS infrastructure.
Mitigation strategies for this vulnerability require immediate action due to its nature as an unpatched third-party contribution. The most effective remediation is to disable and uninstall the REST/JSON module entirely, especially since it is not covered by Drupal's security policy and may lack ongoing maintenance. Administrators should audit their site modules and replace any functionality provided by this specific version with supported alternatives or core features where possible. If retaining similar functionality is necessary, organizations must implement strict rate limiting on API endpoints to slow down enumeration attempts and deploy Web Application Firewalls configured to detect patterns indicative of user enumeration attacks. Additionally, ensuring that error messages returned via the REST interface are generic and do not reveal specific details about whether a username exists or why an authentication attempt failed can mitigate the risk until a secure alternative is implemented. Regular security audits and penetration testing should be conducted to identify similar information disclosure flaws in other custom integrations within the Drupal environment.