What does macOS kernel return 0x10000011 (MACH_SEND_INVALID_TRAILER) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: A supplied Mach message trailer has an unsupported format or privilege.

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MACH_SEND_INVALID_HEADER	MACH_SEND_INVALID_CONTEXT

MACH_SEND_INVALID_TRAILER

Why ordinary clients should rarely see this

MACH_SEND_INVALID_TRAILER is tied to MACH_SEND_TRAILER, an option that lets a privileged sender provide formatted message attributes rather than letting the kernel create the receive-style trailer. The reference interface states that the supplied trailer must match the latest supported kernel format and that the intended use is specialized; ordinary user processes generally should not synthesize one.

A stale kernel-private structure, a trailer appended at the wrong address, an incorrect size, or missing privilege can all lead to this result. This is not a generic payload-validation error, and retrying unchanged data does not help. The correct response is usually to remove the manual trailer path or update the component whose job is to mirror kernel message attributes.

How to diagnose

Confirm that MACH_SEND_TRAILER is actually needed; most user-mode IPC should not set it.
Check the trailer version, size, placement after the message, and the distinction between message size and trailer size.
Verify the caller’s privilege model instead of attempting to bypass the kernel-generated trailer.
Keep kernel-private IPC code tied to the exact supported XNU interfaces for the target system.

References

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