CVE-2013-1946 in RESTWS
Summary
by MITRE
The RESTful Web Services (RESTWS) module 7.x-1.x before 7.x-1.3 and 7.x-2.x before 7.x-2.0-alpha5 for Drupal, when page caching is enabled and anonymous users are assigned RESTWS permissions, allows remote attackers to cause a denial of service via a GET request with an HTTP Accept header set to a non-HTML type, which can "interfere with Drupal's page cache."
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Analysis
by VulDB Data Team • 05/09/2026
The vulnerability described in CVE-2013-1946 represents a critical denial of service weakness within the Drupal RESTful Web Services module that affects versions 7.x-1.x prior to 7.x-1.3 and 7.x-2.x prior to 7.x-2.0-alpha5. This flaw specifically manifests when the Drupal page caching mechanism is enabled alongside anonymous user permissions for RESTWS functionality, creating a condition where malicious actors can exploit the system's caching behavior to disrupt normal service operations. The vulnerability operates through a seemingly innocuous HTTP GET request that includes an Accept header specifying a non-HTML content type, which triggers unexpected behavior in the caching layer.
The technical exploitation of this vulnerability leverages the interaction between Drupal's page caching system and the RESTWS module's handling of content negotiation. When anonymous users possess RESTWS permissions and the system is configured with page caching enabled, the module fails to properly account for non-HTML content types in its caching logic. This creates a scenario where requests with Accept headers specifying formats other than HTML cause the system to process these requests through the full Drupal bootstrap sequence instead of utilizing cached responses. The flaw essentially allows attackers to bypass the intended caching behavior, forcing the system to regenerate page content for each malicious request rather than serving pre-computed cached versions.
The operational impact of this vulnerability extends beyond simple service disruption to potentially overwhelm system resources and degrade performance for legitimate users. When exploited at scale, the denial of service condition can consume significant server CPU cycles and memory resources as the system processes each malicious request through the full Drupal execution path instead of utilizing cached responses. This behavior directly violates the fundamental principles of resource efficiency that caching mechanisms are designed to provide, effectively turning the caching system into a performance bottleneck rather than an optimization tool. The vulnerability particularly affects systems that rely heavily on page caching for performance optimization, making it a serious concern for high-traffic Drupal installations.
This vulnerability aligns with CWE-400, which categorizes it as a "Uncontrolled Resource Consumption" or "Denial of Service" weakness, and demonstrates how improper handling of resource allocation can lead to system degradation. From an ATT&CK framework perspective, this represents a privilege escalation and resource exhaustion technique that can be categorized under T1499.004 for Network Denial of Service, where the attacker leverages existing permissions to cause system instability. The vulnerability also reflects broader security principles related to input validation and proper resource management within web application frameworks, as it shows how seemingly benign HTTP headers can be weaponized to exploit caching mechanisms. Organizations should implement immediate mitigations including updating to patched versions of the RESTWS module, disabling RESTWS permissions for anonymous users when page caching is enabled, or implementing rate limiting mechanisms to prevent abuse of this vulnerability. The issue underscores the importance of comprehensive security testing of caching mechanisms and the potential for denial of service conditions to arise from unexpected interactions between different system components.
The remediation approach for this vulnerability requires careful consideration of the affected Drupal installation's configuration and security requirements. System administrators should prioritize updating to the patched versions of the RESTWS module as specified in the advisory, while also reviewing and adjusting user permission settings to ensure that anonymous users do not possess unnecessary RESTWS capabilities. Additionally, implementing proper input validation and header handling within the web application layer can provide additional protection against similar exploitation patterns. Organizations should also consider monitoring for unusual patterns in HTTP Accept header usage that might indicate exploitation attempts, as this vulnerability can be effectively detected through network traffic analysis and log monitoring systems. The incident highlights the critical need for security professionals to understand how caching mechanisms can introduce unexpected attack vectors and the importance of thorough testing of security controls in complex web application environments.