HRESULT 0x80090309 (SEC_E_CANNOT_PACK): meaning and diagnosis

Status / error code:

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Constant name:

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Description:

The security package is not able to marshall the logon buffer, so the logon attempt has failed

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SEC_E_INVALID_TOKEN	SEC_E_QOP_NOT_SUPPORTED

SEC_E_CANNOT_PACK

SEC_E_CANNOT_PACK signals this condition: The security package could not marshal the logon buffer. The package could not prepare the credential or logon data in the format required for authentication. This normally requires application-level diagnostics rather than a password reset.

What to check

Log the package, credential type, and calling API at the failure point without recording secret values.
Verify that the caller passed the correct structure version and data sizes for the selected package.
Check for code that crosses architecture, serialization, or impersonation boundaries before the SSPI call.

Microsoft: SSPI status codes

Microsoft: InitializeSecurityContext

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