Newest Post: VoidShell Library: Destiny Notes

Good afternoon, readers. Oh yeah, this is going to be the first blog entry of 2026, so let us begin by talking about the VoidShell library's future. As many of you can guess, this library initially started as an ASM x86 program inside a ST file, which was loaded by the engine through a SuperNull exploit (The StateDef Overflow engine vulnerability was used as main vector back then), and despite you could expect, it was simpler than the current version. "Eikidankai" was the first name given to said library and early build versions were used on a few known characters (such as x00x00x or Void.Schmelze) to withstand most SuperNull enemies from the past decade. However, there was no real defense behind it, as it just seals most of the engine vulnerabilities while hooking some primary functions, causing their exploits to be effectively blocked but also rendering them unstable. They were eventually left as PoC characters while the Eikidankai program had to be reworked from scrat...
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M.U.G.E.N Engine Researches: State Filepath Overflow

Good evening, readers. 
It has been a while since the last blog entry was created, but well, life things.

For this occassion, we are going to talk about the latest vulnerability discovered in M.U.G.E.N Engine, which has been used by SuperNull characters like "On The Verge of Death" or "Qvorda", so let's begin.

State Filepath Overflow, also known as "STBOF" or "ST.Path", is an engine vulnerability that allows for arbitrary code execution during character selection, making it a good alternative to use for SuperNull characters.

The discovery of this vulnerability was born out of Nomi's ideas about trying to overflow the ST Filepath textline in WinMUGEN, which was impossible to perform, as only 255 bytes can be used per text string.

However, it could feasibly be used on the 1.xx engine versions due to their increased textline size limit(4095 bytes), so I decided to investigate it further.

"St" is the entry filepath the engine uses to load Constants/States before St0 ~ St9, so it cannot be omitted, as doing so will cause the engine to raise an error message.

The most interesting detail about this filepath section is that when any state file except for the character's definition file is placed, the engine will copy the source filepath into a buffer with no max size limit before loading, which renders it vulnerable to buffer overflow.

M.U.G.E.N Engine being debugged

After investigating the possibilities of a buffer overflow attack, I have finally noticed 0xB04 bytes(1.1b only) were necessary to overwrite the parser's return address, resulting in arbitrary code execution.

Yet, a ROP chain is required in order to make your shellcode executable before jumping into it, as the NX Bit is enabled by default in these engine versions, so reusing the stack region for pivoting is a good idea.

At this point, shellcode should be executed with no problem, as this character was used as Proof-of-Concept for it:

Qvorda's Exploit
A code template that uses the engine vulnerability can be downloaded via this blog entry.
Well, this is all for today. Have a nice day.

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