CVE-2016-3092 in Knowledge
Summary
by MITRE
The MultipartStream class in Apache Commons Fileupload before 1.3.2, as used in Apache Tomcat 7.x before 7.0.70, 8.x before 8.0.36, 8.5.x before 8.5.3, and 9.x before 9.0.0.M7 and other products, allows remote attackers to cause a denial of service (CPU consumption) via a long boundary string.
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Analysis
by VulDB Data Team • 04/16/2025
The vulnerability identified as CVE-2016-3092 represents a critical denial of service flaw within the MultipartStream class of Apache Commons Fileupload library. This vulnerability affects multiple versions of Apache Tomcat and other products that rely on this component for handling multipart form data processing. The flaw specifically targets the boundary string handling mechanism that is fundamental to parsing multipart HTTP requests commonly used for file uploads. Attackers can exploit this weakness by crafting malicious multipart requests containing excessively long boundary strings, which causes the affected systems to consume excessive CPU resources during the parsing process.
The technical implementation of this vulnerability stems from inadequate input validation and inefficient boundary string processing within the MultipartStream class. When the system encounters a multipart request with an unusually long boundary string, the parsing algorithm enters into an inefficient loop where it continuously searches for the boundary pattern in the input data. This creates a computationally expensive operation that can consume significant CPU cycles and memory resources, effectively leading to a denial of service condition. The vulnerability is particularly dangerous because it can be triggered through normal HTTP request processing without requiring authentication or special privileges, making it easily exploitable in public-facing web applications.
The operational impact of CVE-2016-3092 extends beyond simple service disruption to potentially affect entire web application availability and system performance. When exploited, the vulnerability can cause servers to become unresponsive or significantly slow down processing capabilities, impacting legitimate users and potentially allowing attackers to perform resource exhaustion attacks. This vulnerability affects a wide range of Apache Tomcat versions including 7.x, 8.x, 8.5.x, and 9.x series, making it particularly widespread across enterprise environments that rely on these application servers for hosting web applications. The vulnerability aligns with CWE-770, which describes allocation of resources without limits or with inadequate limits, and represents a classic example of a resource exhaustion attack pattern that can be mapped to ATT&CK technique T1499.1 for resource exhaustion.
Organizations affected by this vulnerability should prioritize immediate patching of their Apache Tomcat installations to version 7.0.70 or later, 8.0.36 or later, 8.5.3 or later, and 9.0.0.M7 or later respectively. Additionally, implementing request size limits and boundary string length validation at the web server level can provide additional defense-in-depth measures. Network-level protections such as rate limiting and monitoring for unusual CPU consumption patterns can help detect exploitation attempts. The vulnerability demonstrates the importance of proper input validation and resource management in security-critical components, highlighting how seemingly simple parsing operations can become attack vectors when not properly constrained. Organizations should also consider implementing application firewalls or intrusion prevention systems that can detect and block malformed multipart requests before they reach the vulnerable components.