CVE-2016-20049 in JAD Java Decompiler
Summary
by MITRE • 03/28/2026
JAD 1.5.8e-1kali1 and prior contains a stack-based buffer overflow vulnerability that allows attackers to execute arbitrary code by supplying oversized input that exceeds buffer boundaries. Attackers can craft malicious input strings exceeding 8150 bytes to overflow the stack, overwrite return addresses, and execute shellcode in the application context.
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Analysis
by VulDB Data Team • 03/29/2026
The vulnerability identified as CVE-2016-20049 represents a critical stack-based buffer overflow in JAD 1.5.8e-1kali1 and earlier versions of the Java Decompiler application. This flaw exists within the application's input processing mechanism where insufficient boundary checking allows maliciously crafted input to exceed allocated buffer space. The vulnerability specifically affects the handling of input strings that exceed 8150 bytes, creating a condition where stack memory can be overwritten through controlled input manipulation. The buffer overflow occurs during the decompilation process when JAD processes malformed or excessively long input parameters, making this a particularly dangerous vulnerability given the application's role in software analysis and reverse engineering activities.
The technical implementation of this vulnerability stems from improper input validation within the JAD decompiler's parsing routines. When processing input data exceeding the allocated buffer size, the application fails to perform adequate bounds checking, allowing memory corruption to occur at the stack level. The specific threshold of 8150 bytes indicates a well-defined overflow point where the application's internal buffers cannot accommodate the input data, leading to stack memory overwrite. This memory corruption directly affects the return address stored on the stack, enabling attackers to manipulate the program's execution flow. The vulnerability maps to CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue that has been consistently identified as a primary attack vector in software security assessments. The attack vector operates through direct manipulation of stack memory through controlled input sequences that trigger the buffer overflow condition.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with complete control over the application's execution context. When successfully exploited, the buffer overflow allows for arbitrary code execution with the privileges of the user running the JAD application, potentially enabling privilege escalation attacks or system compromise. The vulnerability is particularly concerning in environments where security professionals rely on JAD for legitimate reverse engineering activities, as attackers could exploit this weakness to gain unauthorized access to sensitive code analysis environments. The attack requires minimal sophistication since it involves crafting input strings exceeding the buffer limit, making it accessible to attackers with basic knowledge of buffer overflow exploitation techniques. This vulnerability also aligns with ATT&CK technique T1059.007 Command and Scripting Interpreter: Visual Basic, as the exploitation could occur through automated scripts that generate the oversized input strings to trigger the stack overflow.
Mitigation strategies for CVE-2016-20049 should focus on immediate application updates and input validation improvements. The primary recommendation involves upgrading to JAD versions that have implemented proper buffer size checking and input validation mechanisms. Security administrators should also implement network segmentation and access controls to limit exposure of vulnerable systems. Additional defensive measures include deploying input sanitization filters that can detect and block oversized input sequences before they reach the vulnerable application. The vulnerability highlights the importance of proper memory management practices in software development, particularly for applications that process external input data. Organizations should also consider implementing runtime protections such as stack canaries or address space layout randomization to make exploitation more difficult even if the underlying vulnerability persists. Regular security assessments and code reviews should be conducted to identify similar buffer overflow vulnerabilities in other applications within the organization's infrastructure.