[Research] RCE 0-day : Immunity Debugger

Over four years ago, at JennyLab, we identified a previously unknown zero-day vulnerability in Immunity Debugger, which has remained unreported to this day. This critical security flaw enables arbitrary code execution, allowing an attacker to run a binary without triggering Immunity Debugger’s debugging mode.

The implications of this vulnerability are significant. It can be leveraged to bypass the analysis of potentially malicious code samples, effectively preventing security researchers from examining the behavior of malware. Moreover, it poses a direct threat to researchers themselves, as it could be used to compromise their machines, potentially gaining unauthorized access to sensitive data or sabotaging their investigative efforts.

This discovery underscores the importance of rigorous security assessments in tools widely used within the cybersecurity community, as even trusted software can harbor vulnerabilities with far-reaching consequences.

The exploitation of this vulnerability is thoroughly documented in the "main.c" file is part of the open source tool "cr1m3". The vulnerability is specifically triggered by defining and manipulating the functions "WinMain()" and "WinMainCRTStartup()", which subsequently return control to the "main()" function.

This process effectively exploits the program’s execution flow, enabling the attacker to bypass normal debugging operations. By leveraging these entry points, it becomes possible to execute malicious code without the debugger entering its intended operational state. This approach demonstrates how subtle weaknesses in function handling can be weaponized to undermine critical security tools like Immunity Debugger.