What does BSOD 126 (SYSTEM_THREAD_EXCEPTION_NOT_HANDLED) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: SYSTEM_THREAD_EXCEPTION_NOT_HANDLED identifies a Windows bug check whose dump parameters and stack determine the failing component.

Could be also:
Constant	Type	OS
ERROR_MOD_NOT_FOUND	Win32 error	Windows
EADDRNOTAVAIL	errno	Solaris
ENOTCONN	errno	Windows

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SYSTEM_THREAD_EXCEPTION_NOT_HANDLED

The SYSTEM_THREAD_EXCEPTION_NOT_HANDLED bug check has a value of 0x0000007E. This bug check indicates that a system thread generated an exception that the error handler did not catch.

Important

SYSTEM_THREAD_EXCEPTION_NOT_HANDLED parameters

Parameter	Description
1	The exception code that was not handled.
2	The address where the exception occurred.
3	The address of the exception record.
4	The address of the context record.

Cause for SYSTEM_THREAD_EXCEPTION_NOT_HANDLED

This bug check indicates that a system thread generated an exception that the error handler did not catch. For SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, to interpret it, you must identify which exception was generated.

Common exception codes include the following:

0x80000002: STATUS_DATATYPE_MISALIGNMENT indicates an unaligned data reference was encountered.
0x80000003: STATUS_BREAKPOINT indicates a breakpoint or ASSERT was encountered when no kernel debugger was attached to the system.
0xC0000005: STATUS_ACCESS_VIOLATION indicates a memory access violation occurred.

For a complete list of exception codes, see NTSTATUS values. The exception codes are defined in ntstatus.h and apply directly when investigating SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, a header file provided by the Windows Driver Kit. For SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, (For more info, see Header files in the Windows Driver Kit).

Resolution for SYSTEM_THREAD_EXCEPTION_NOT_HANDLED

If you plan to debug this problem, the exception address (parameter 2) should identify the driver or function that caused this problem.

For SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, if a driver is listed by name within the bug check message, disable or remove that driver. If the issue is narrowed down to a single driver, set breakpoints and single-step forward in code to locate the failure and gain insight into events leading up to the crash.

For SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, The !analyze debugger extension displays information about the bug check and can be helpful in determining the root cause.

Additional analysis can be done by using the !thread extension, as well as the dds, dps, and dqs (display words and symbols) commands. This can be a reasonable technique when WinDbg reports "Probably caused by : ntkrnlmp.exe."

If exception code 0x80000003 occurs, a hard-coded breakpoint or assertion was hit, but the system was started with the /NODEBUG switch. This problem should not occur frequently. If it occurs repeatedly, make sure that a kernel debugger is connected and the system is started with the /DEBUG switch.

For SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, if exception code 0x80000002 occurs, the trap frame supplies additional information.

For more information about WinDbg and !analyze, see the following topics:

Analyze crash dump files by using WinDbg
Analyzing a kernel-mode dump file with WinDbg
Using the !analyze extension and !analyze

Remarks for SYSTEM_THREAD_EXCEPTION_NOT_HANDLED

If you are not equipped to use the Windows debugger to work on this problem, you should use some basic troubleshooting techniques:

Check the System Log in Event Viewer for additional error messages that might help identify the device or driver that is causing bug check 0x7E.
For SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, if a driver is identified in the bug check message, disable the driver or check with the manufacturer for driver updates.
Check with your hardware vendor for any ACPI or other firmware updates. Hardware issues, such as system incompatibilities, memory conflicts, and IRQ conflicts can also generate this error.
You can also disable memory caching/shadowing of the BIOS to try to resolve the error. Also run hardware diagnostics that the system manufacturer supplies.
For SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, confirm that any new hardware that is installed is compatible with the installed version of Windows. For example, you can get information about hardware required for a system affected by SYSTEM_THREAD_EXCEPTION_NOT_HANDLED at Windows 10 Specifications.

For SYSTEM_THREAD_EXCEPTION_NOT_HANDLED, for additional general troubleshooting information, see Blue screen data.

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