CVE-2016-20007 in REST-JSON Project
Summary
by MITRE • 01/01/2021
The REST/JSON project 7.x-1.x for Drupal allows session name guessing, 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 • 09/28/2026
The vulnerability identified as SA-CONTRIB-2016-033 within the REST/JSON module for Drupal version 7.x-1.x represents a critical session management flaw that facilitates unauthorized access through session identifier prediction. This issue stems from an improper implementation of session handling mechanisms, specifically allowing attackers to guess or predict valid PHP session names used by the application. In standard web applications, session identifiers are intended to be cryptographically secure random strings generated by the server to maintain stateful interactions with authenticated users. However, in this specific module version, the generation logic fails to adhere to sufficient entropy requirements, rendering the session tokens predictable and susceptible to brute-force or statistical analysis attacks.
From a technical perspective, this flaw aligns closely with CWE-330, which describes the use of insufficiently random values, and CWE-614, concerning sensitive cookies in sessions without proper validation. The REST/JSON module interacts heavily with external clients via API endpoints, often requiring authentication to access protected resources. When a user authenticates, the server assigns a session cookie containing the session identifier. If this identifier is predictable due to weak random number generation or flawed seeding mechanisms within the PHP environment as utilized by this specific Drupal contrib project, an attacker can iterate through potential session IDs until they find one that corresponds to an active authenticated session. This bypasses traditional authentication controls entirely because the server trusts any valid-looking session ID presented in subsequent requests without verifying its origin or integrity beyond basic format checks.
The operational impact of this vulnerability is severe, particularly for sites relying on this module for headless content management or API-driven integrations. An attacker who successfully guesses a valid session identifier gains full access to the associated user account with all its privileges. If the targeted account possesses administrative rights, which are common in Drupal environments used by developers and site administrators testing REST endpoints, the consequences escalate rapidly to complete system compromise. The attacker can then modify content, inject malicious scripts via stored cross-site scripting vectors enabled through admin panels, exfiltrate sensitive database records, or install backdoors for persistent access. This effectively neutralizes the security boundary provided by Drupal's core authentication framework, turning a standard web application into an open target for privilege escalation and data theft.
This vulnerability is also relevant to MITRE ATT&CK technique T1078, Valid Accounts, specifically in the context of credential-based attacks where valid session tokens are harvested or predicted rather than stolen via phishing or keylogging. It further relates to T1528, Steal Application Access Token, as the session ID functions similarly to an access token for stateful API interactions. The lack of coverage under Drupal's official security advisory policy highlights a common risk in open-source ecosystems where contrib modules may not receive the same rigorous review and patching cadence as core software. Organizations using this module must recognize that their exposure is higher than standard Drupal installations due to both the technical flaw and the reduced support visibility.
Mitigation strategies for this vulnerability require immediate action since automated patches from official channels are unavailable or delayed given its status outside the main security advisory scope. The primary recommendation is to disable or uninstall the REST/JSON module if it is not strictly necessary, thereby removing the attack vector entirely. If the functionality provided by the module is essential, administrators should upgrade to a patched version of the project that addresses the session generation logic, ensuring that cryptographically secure random number generators are utilized for creating session identifiers. Additionally, implementing strict input validation and enforcing multi-factor authentication can add layers of defense that mitigate the impact even if an attacker manages to guess a session ID. Regular security audits focusing on third-party module integrity and adherence to OWASP Session Management best practices are also advised to prevent similar weaknesses in other parts of the application stack.