CVE-2014-7191 in Node.js
Summary
by MITRE
The qs module before 1.0.0 in Node.js does not call the compact function for array data, which allows remote attackers to cause a denial of service (memory consumption) by using a large index value to create a sparse array.
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Analysis
by VulDB Data Team • 02/21/2022
The qs module vulnerability CVE-2014-7191 represents a critical denial of service weakness in Node.js applications that process query string data. This vulnerability specifically affects versions of the qs module prior to 1.0.0 and stems from an improper handling of array data structures during query string parsing operations. The flaw manifests when attackers craft malicious query strings containing large index values that create sparse arrays within the parsing process. These sparse arrays consume excessive memory resources as the parser attempts to allocate memory for array elements that are not actually populated, leading to uncontrolled memory growth and eventual system exhaustion.
The technical root cause of this vulnerability aligns with CWE-400, which categorizes improper handling of resource identifiers or index values in array operations. When the qs module processes query strings, it fails to invoke the compact function for array data structures, allowing sparse array creation without proper memory management. This design flaw enables attackers to exploit the parsing mechanism by injecting query parameters with excessively large numeric indices, such as ?a[1000000]=value, where the parser allocates memory for 1,000,000 array elements despite only requiring one actual value. The absence of proper bounds checking and sparse array compaction results in exponential memory consumption proportional to the largest index value provided.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can severely compromise application availability and system stability. Attackers can exploit this weakness to consume massive amounts of memory resources, potentially causing application crashes, system slowdowns, or complete system hangs. In web applications, this vulnerability can be leveraged to launch resource exhaustion attacks against servers handling query string data, making it particularly dangerous in high-traffic environments. The vulnerability is classified under the MITRE ATT&CK framework as a resource exhaustion technique, specifically targeting memory consumption through malformed input processing. When exploited in web applications, this vulnerability can affect multiple system components including web servers, application servers, and database connections, potentially leading to cascading failures across interconnected services.
Mitigation strategies for CVE-2014-7191 require immediate version updates to the qs module, specifically upgrading to version 1.0.0 or later where the compact function is properly invoked for array data structures. Organizations should implement input validation measures to filter out or reject query strings containing excessively large index values, particularly those exceeding reasonable thresholds such as 10000 or 100000 elements. Additionally, implementing rate limiting and request size restrictions can help prevent exploitation attempts by limiting the volume of potentially malicious data processed per request. System administrators should monitor memory consumption patterns and implement automated alerting for unusual memory usage spikes that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper array handling in parsing libraries and underscores the necessity of thorough testing for resource consumption patterns in input processing functions, particularly in applications handling user-supplied data through query strings or similar structured data formats.