BSOD 0x5B (SET_ENV_VAR_FAILED): causes and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: Windows could not set a required environment variable during system initialization.

Could be also:
Constant	Type	OS
EPROTOTYPE	errno	Linux
ENOMSG	errno	Mac
ERESTART	errno	Solaris

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CRITICAL_SERVICE_FAILED	HAL_INITIALIZATION_FAILED

SET_ENV_VAR_FAILED

Startup environment-variable setup failure for SET_ENV_VAR_FAILED

SET_ENV_VAR_FAILED is bug check code 0x0000005B.

This historical initialization bug check indicates that the kernel or session startup path failed while building required environment state. It is not the same as an application failing to set a user environment variable after logon.

How to read it in a dump

Check the boot phase and the process/session context in the dump.
The nested status code, if present, is more important than the symbolic name.
Registry hive corruption, memory pressure, or early subsystem failure can be the underlying cause.

What to check

Inspect system hive and session-manager related errors in boot logs.
Check whether the failure followed an OS update, security product change, or registry modification.
Collect a kernel or full dump because small dumps may not contain enough startup state.

References

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