CVE-2026-96377 in Combined Image Style
Summary
by MITRE • 10/22/2026
Allocation of Resources Without Limits or Throttling vulnerability in Drupal Combined image style allows Excessive Allocation. This issue affects Combined image style versions: from 0.0.0 to 1.0.7.
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Analysis
by VulDB Data Team • 10/22/2026
The vulnerability identified as an allocation of resources without limits or throttling within the Drupal Combined Image Style module represents a significant resource exhaustion risk for web applications relying on this functionality. This flaw specifically impacts version ranges from 0.0.0 up to and including 1.0.7, affecting systems that utilize dynamic image processing capabilities provided by the module. The core issue stems from the absence of adequate constraints on the computational resources allocated during the generation or manipulation of combined images. When a user requests an image style combination, the server processes the request without verifying whether the operation will consume excessive memory, CPU cycles, or disk I/O bandwidth relative to system capacity. This lack of throttling allows for the potential creation of denial-of-service conditions through resource exhaustion rather than traditional network flooding techniques.
From a technical perspective, this vulnerability aligns with CWE-770: Allocation of Resources Without Limits or Throttling in the Common Weakness Enumeration database. The flaw occurs because the module fails to implement safeguards such as maximum pixel dimensions, timeout limits for image processing scripts, or memory usage caps before initiating heavy computational tasks. In Drupal environments, image styles often involve complex operations like resizing, cropping, and applying filters which can be computationally intensive. Without proper bounds checking, an attacker can craft specific requests that trigger these processes with parameters designed to maximize resource consumption. For instance, requesting a combination of high-resolution images or multiple overlapping transformations can cause the PHP process handling the request to consume all available memory on the server, leading to application crashes or system instability.
The operational impact of this vulnerability is primarily centered around service availability and performance degradation. An attacker exploiting this flaw does not need to inject malicious code or gain unauthorized access to sensitive data; instead, they can simply overwhelm the target infrastructure with legitimate-looking but resource-intensive requests. This results in a denial-of-service scenario where legitimate users are unable to access the website due to server overload. Furthermore, repeated exploitation attempts can lead to increased hosting costs if the environment is cloud-based and billed by usage metrics such as CPU time or memory allocation. The vulnerability also poses indirect risks to system integrity, as frequent crashes may corrupt temporary files or leave database connections in an inconsistent state, requiring manual intervention to restore normal operations.
Mitigation strategies for this vulnerability involve both immediate patching and long-term architectural improvements. Administrators should immediately upgrade the Combined Image Style module to a version newer than 1.0.7 where these resource limits have been implemented by the developers. In cases where upgrading is not immediately feasible, temporary mitigations include configuring web server settings such as Nginx or Apache to limit request sizes and timeouts for image processing endpoints. Additionally, implementing rate limiting at the load balancer or reverse proxy level can help throttle excessive requests from single IP addresses before they reach the application layer. It is also advisable to review PHP configuration parameters like memory_limit and max_execution_time to ensure they are set appropriately high enough to handle legitimate traffic but low enough to prevent runaway processes from consuming all system resources.
This vulnerability maps to several techniques in the MITRE ATT&CK framework, particularly T1496: Resource Hijacking or more broadly under Denial of Service tactics where availability is compromised through resource exhaustion. Security teams should monitor server logs for unusual spikes in image processing requests and look for patterns indicative of automated scanning tools targeting Drupal sites with known vulnerable modules. Regular vulnerability assessments and penetration testing focused on input validation and resource management are essential to identify similar weaknesses across the entire application stack, ensuring that no other components suffer from analogous flaws related to unbounded resource allocation.