CVE-2012-5537 in Simplenews Scheduler
Summary
by MITRE
The Simplenews Scheduler module 6.x-2.x before 6.x-2.4 for Drupal allows remote authenticated users with the "send scheduled newsletters" permission to inject arbitrary PHP code into the scheduling form, which is later executed by cron.
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Analysis
by VulDB Data Team • 03/17/2019
The vulnerability identified as CVE-2012-5537 resides within the Simplenews Scheduler module version 6.x-2.x of the Drupal content management system prior to version 6.x-2.4. This security flaw represents a critical code injection vulnerability that affects the module's handling of user input within the newsletter scheduling functionality. The vulnerability specifically impacts environments where the Simplenews Scheduler module is installed and configured with user permissions that allow for newsletter scheduling operations.
The technical implementation of this vulnerability stems from insufficient input validation and sanitization within the scheduling form processing logic. When authenticated users with the specific permission "send scheduled newsletters" submit data through the newsletter scheduling interface, the module fails to properly sanitize user-supplied input before storing it for later execution during cron processing. This inadequate sanitization creates a path for malicious code injection where attackers can embed arbitrary PHP code within the scheduling form fields. The vulnerability is particularly concerning because the injected code is executed during the cron job execution phase, which typically runs with elevated privileges and system-level access.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with potential access to sensitive system resources and data within the Drupal environment. Since the execution occurs during cron processing, attackers can leverage this vulnerability to perform actions such as data exfiltration, system reconnaissance, privilege escalation, or even complete system compromise depending on the execution context and available permissions. The vulnerability affects all Drupal 6.x installations using the affected Simplenews Scheduler module version, making it a widespread concern for organizations maintaining legacy Drupal systems. This type of vulnerability aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and represents a classic example of how insufficient input validation can lead to arbitrary code execution.
The attack vector requires an authenticated user with specific permissions, which means that exploitation is limited to users who already have access to the Drupal system. However, this requirement does not diminish the severity of the vulnerability, as it represents a privilege escalation path that allows attackers to execute arbitrary code with potentially elevated privileges. The vulnerability also demonstrates a failure in the principle of least privilege, as the module does not properly isolate user input from system execution contexts. Organizations should consider this vulnerability in the context of ATT&CK framework tactic TA0002 (Execution) and technique T1059.001 (Command and Scripting Interpreter: PowerShell) as it enables similar execution patterns within the web application environment. The vulnerability's persistence through cron execution makes it particularly dangerous as it can continue to execute malicious code without requiring repeated user interaction, potentially allowing for long-term system compromise.
Mitigation strategies should include immediate application of the security patch released by the Drupal community for version 6.x-2.4 of the Simplenews Scheduler module. Organizations should also implement proper input validation and sanitization practices throughout their Drupal installations, particularly for modules that handle user input in system-critical contexts. Network segmentation and privilege separation should be implemented to limit the potential impact of successful exploitation, while regular security audits and vulnerability assessments should be conducted to identify similar issues in other modules. Additionally, organizations should consider implementing web application firewalls and input filtering mechanisms to detect and prevent malicious code injection attempts, as well as maintaining updated security monitoring systems to detect anomalous cron execution patterns that might indicate exploitation of this vulnerability.