Detect, analyze and uniquely identify crashes in Windows applications
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Detect, analyze and uniquely identify application bugs.


Do you...

  • want to know what kind of bug is causing an application to crash?
  • want to know if a bug might be security vulnerability?
  • want to find out if two or more crashes are caused by the same bug?
  • want a human readable report with an analysis of a bug?

...then BugId may be for you!

Quick setup

To use BugId, please download and install the following software:

If you install Python and Debugging Tools for Windows with their default settings, BugId should be able to run without adjusting any settings. You can unzip BugId anywhere you want on your local file system.

Before you start BugId, you should enable full page heap in the target application. This can be done per binary by setting certain Global Flags. The easiest way to do this is to use the pageheap.cmd script that comes with BugId. For instance, to enable full page heap for notepad, run the following command:

C:\BugId>pageheap notepad.exe ON

(Note that this command must be run from an elevated command-prompt with administrative access to the machine).

To make things even easier, pageheap.cmd has a list of known applications. You can enable or disable full page heap for any one of them by providing its name, e.g. pageheap msie ON enables full page heap for Microsoft Internet Explorer. Use pageheap /? to get more information about command-line arguments.

At this point, you may want to test if BugId is working correctly. We can do this by running an application in BugId and crashing it to see if BugId reports the bug correctly. A good application to use for this test is rundll32.exe which is found on all Windows installations in the system32 sub-folder of the Windows folder (%WinDir%). It can be used to load any dll found on the local file system and call an exported function in this dll with a certain call format. There are many dlls in the system32 folder that export functions. Most of these exported functions expect arguments in a completely different format than what rundll32 will provide, causing the application to crash.

First we must turn on full page heap in rundll32 with the following command:

C:\BugId>pageheap rundll32.exe ON

Next we will start BugId and tell it to start rundll32 with arguments that instruct it to load advapi32.dll and call CloseThreadWaitChainSession. At the time of this writing that causes a so-called NULL pointer access violation, which BugId should detect and report.

C:\BugId>BugId.cmd %WinDir%\system32\rundll32.exe -- advapi32 CloseThreadWaitChainSession

Notice there is a -- between rundll32.exe and the arguments passed to it. This is because you may want to provide arguments to both BugId itself and the application you want to test. These two sets of arguments should be separated by -- on the command-line. Everything before -- is handled by BugId and everything after is ignored by BugId but passed to the application.

If all is well, the output of BugId will look like this:

* Command line: C:\WINDOWS\system32\rundll32.exe advapi32 CloseThreadWaitChainSession
+ Main process 8024/0x1F58 (rundll32.exe): Attached; command line = C:\WINDOWS\system32\rundll32.exe advapi32 CloseThreadWaitChainSession.
,-- A bug was detect in the application ----------------------------------------
| Id @ Location:    AVR@NULL a1f.904 @ rundll32.exe!advapi32.dll!WctRemoveEntry
| Description:      Access violation while reading memory at 0x0 using a NULL pointer.
| Security impact:  Denial of Service
| Version:          rundll32.exe 10.0.16299.15 (x64)
|                   advapi32.DLL 10.0.16299.15 (x64)
| Bug report:       AVR@NULL a1f.904 @ rundll32.exe!advapi32.dll!WctRemoveEntry.html (60703 bytes)

The first line tells you the command-line BugId is going to start. The second line tells you that this caused a new process to be created with process id 8024, running rundll32.exe and the command line for this process (which is of course the same as in the first line). Soon after starting the application, a bug was detected. BugId generated a unique id (AVR@NULL a1f.904) for this bug and reported its location is in the WctRemoveEntry function of the advapi32.dll dll loaded by rundll32.exe. Since NULL pointer crashes are normally not exploitable other than to crash the application, the bug's security impact is Denial of Service. BugId by default generates a HTML formatted report for every bug it finds and tells you the location where this report was stored. As you can see, the file name of the report is based on the bug id and location.

Every bug id generated by BugId consists of two part separated by a space. The first part describes the type of bug. In the above example, AVR@NULL, this means Access Violation Reading memory at address NULL. The second part describes the location of the bug; it consists of two short hashes separated by a dot. These hashes are calculated from the top functions on the stack that are considered relevant to the bug. In the example, a1f.904 consists of a1f (calculated from advapi32.dll!WctRemoveEntry) and 904 (calculated from advapi32.dll!CloseThreadWaitChainSession).

If you run that same command again, BugId will report the exact same BugId, as this should couse the exact same bug in the exact some code.

Congratulations! You are now ready to test your own crashes with BugId, but you may want to run BugId.cmd --help at some point to get information about the many different command-line options BugId supports.


BugId is free for non-commercial use and commercial licenses are available. BugId has a 30 day trial period after which a valid license is required. Commercial licenses can be bought and non-commercial licenses requested at

Keep up-to-date with BugId development through the BugId blog page.


BugId has been developed for and tested on a large number of applications during fuzzing to analyze hundreds of thousands of crashes caused by hundreds of different bugs. In this role it has proven to be extremely accurate in analyzing bugs with a very low false positive and negative rate; both are less than 1%.

Of course not all types of bugs are easy to detect and analyze. Some bugs cannot currently be detected reliably at the time they happen but cause a crash much later on in completely unrelated code, leading to a completely incorrect analysis. In such cases, repeatedly reproducing the same bug will lead to a number of different bug ids as the application crashes in different ways at different times. To make sure this is not the case, you are advised to run your test case in BugId a number of times to see if the bug id stays the same.

Others bugs cause crashes that look like they are caused by a different type of bug. This can result in incorrect analysis and bug ids. Most notably, bugs that are the result of bad casts in C/C++ code are currently impossible to detect and report by BugId. They can result in various different types of crashes; most commonly access violations when values stored in properties of an object are incorrectly used as pointers. If you expect bad casts might be the cause of a crash, you should double check the analysis done by BugId to make sure it is correct.

BugId is highly dependent on full page heap being used by the application to be able to detect and analyze a large number of heap related bugs. This means that it will be much less effective at detecting and analyzing bugs in application that use their own internal heap manager that does not rely on the standard Windows heap.


Creative Commons License This work is licensed under a [Creative Commons Attribution-NonCommercial 4.0 International License]( It is provided free of charge for non-commercial use only.

BugId has a trial period to allow you to assess its usefulness. If you want to continue to use BugId after the trial period has ended, you are required to get a license file from On this site you can request a non-commercial license or buy a commercial license.

If you find BugId useful and would like to make a donation in BitCoin, you can send them to 183yyxa9s1s1f7JBpPHPmzQ346y91Rx5DX.