A MIDL_STUBLESS_PROXY_INFO structure holds the client-side marshaling metadata for an interface. It links a proxy to format strings and a stub descriptor so RPC calls can be encoded, decoded and dispatched correctly between client and server processes.
What this structure does in RPC marshalling
MIDL_STUBLESS_PROXY_INFO is part of the client-side glue that lets an RPC interface work without handwritten stubs. It points the proxy at the format strings and stub descriptor the runtime needs so parameters can be marshalled, unmarshalled, and routed correctly across the call boundary.
In practical terms, it sits between the interface definition and the generated proxy code. The structure does not define business logic or access decisions, but it is essential to the mechanics of how an RPC client translates a local function call into an on-the-wire request that the server can understand.
Why it matters for correctness and interoperability
This structure exists to keep client and server in agreement about calling conventions, parameter layout, and type encoding. If the metadata is wrong, the call may fail in ways that look like transport problems, but the real issue is often malformed marshaling metadata or an interface mismatch.
That makes it a low-level correctness dependency rather than a feature in its own right. It matters most when generated code, version drift, or platform differences cause the proxy to interpret the interface differently from the server-side stub.
How it relates to generated proxy and stub code
RPC toolchains typically generate this metadata from an IDL description, then embed it into the client proxy layer. The proxy uses the structure to find the byte-level descriptions of arguments and to locate the stub descriptor that tells the runtime how the interface should be handled.
Because it is generated support data, developers usually do not edit it directly. The operational concern is understanding that the proxy, format strings, and stub descriptor are a linked set: if one piece is inconsistent, the call path can break even when the application code itself appears correct.
Common failure modes and what they usually look like
When this metadata is corrupted, stale, or mismatched to the interface definition, failures often show up as serialization errors, unexpected parameter values, or server dispatch problems. Those symptoms can be hard to diagnose because the application may surface only a generic RPC failure.
Version skew is a common source of trouble. If the client proxy was built from different interface metadata than the server expects, the call may succeed syntactically while still decoding into the wrong structure on the other side.
Risk and Threat Considerations
Marshaling metadata is a trust boundary for RPC. If an attacker can tamper with the proxy metadata or the generated call path, they may be able to confuse parameter handling, trigger crashes, or steer the application into unsafe parsing behavior.
Failure mechanism: Invalid or manipulated format strings and stub descriptors can cause the client and server to disagree about how arguments are encoded, decoded, or dispatched, which can lead to denial of service or memory-safety consequences in poorly hardened components.
Impact: The most likely outcomes are failed remote calls, service instability, and increased exposure to exploitation where the surrounding RPC implementation assumes the metadata is trustworthy.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
MITRE ATT&CK addresses the attack and risk surface, while NIST SP 800-53 Rev 5 sets the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| NIST SP 800-53 Rev 5 | SC-13 — Cryptographic Protection | RPC marshaling metadata protects data in transit between client and server. |
| SI-10 — Information Input Validation | Malformed marshaling metadata creates parsing and decoding failures. | |
| Recommendation — Protect RPC payloads in transit with SC-13 to reduce tampering and exposure risk. Validate interface inputs and generated artifacts under SI-10 before deployment. | ||
| MITRE ATT&CK | T1021 — Remote Services | RPC is a remote service access path whose abuse can support lateral movement. |
| Recommendation — Monitor remote service use under T1021 for anomalous RPC activity and misuse. | ||
Practitioner Guidance
What to watch for: Treat this structure as generated security-sensitive plumbing, not application data. If RPC behavior changes after an IDL update, proxy rebuild, or platform migration, verify that the client proxy and server stub were produced from the same interface definition and that the generated artifacts are being deployed together.
Practitioner takeaway: When RPC issues look inconsistent or interface-specific, inspect the generated marshaling path before chasing transport or business-logic defects.
Related resources from NHI Mgmt Group
Deepen Your Knowledge
Free weekly newsletter
Subscribe to the NHI & AI Identity Journal
The latest on NHI and Agentic AI security – articles, research, breaches, news and events every week.
Bonus 33% off our NHI Course when you subscribe.
Reviewed and updated by the NHIMG editorial team on November 9, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org