BSOD 127 (UNEXPECTED_KERNEL_MODE_TRAP): causes and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: UNEXPECTED_KERNEL_MODE_TRAP the processor generated a trap that the kernel could not handle. Parameter 1 is the trap number; a double fault, commonly trap.

Could be also:
Constant	Type	OS
ERROR_PROC_NOT_FOUND	Win32 error	Windows
ENETDOWN	errno	Solaris
ENOTRECOVERABLE	errno	Windows

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UNEXPECTED_KERNEL_MODE_TRAP

UNEXPECTED_KERNEL_MODE_TRAP meaning

UNEXPECTED_KERNEL_MODE_TRAP is bug check 0x0000007F. The processor generated a trap that the kernel could not handle. Parameter 1 is the trap number; a double fault, commonly trap 8, often points to kernel stack exhaustion or a second fault during exception handling.

How to analyze the result

Decode the trap number, inspect the trap frame and stack, and look for recursive filter-driver paths, stack overrun, CPU or memory faults, overclocking, and mismatched hardware. Multiple dumps help distinguish a stable software stack from random hardware corruption.

Preserve the complete dump, all four parameters, Windows build, loaded modules, and the event timeline before changing drivers or firmware while investigating this result.
Run !analyze -v and follow the parameter-specific objects and the stack associated with this result rather than relying only on the symbolic name or a single probable-cause line.
Compare multiple dumps when available; a stable instruction or object path associated with this result is stronger evidence than a module that appears only after earlier corruption.

Recovery boundary

Correct the driver recursion, stack use, firmware, or hardware condition shown by the trap. Do not assume all 0x7F crashes are memory failures; the trap number and repeated stack pattern are decisive.

Official references

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