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FWP_E_CALLOUT_NOTIFICATION_FAILED
FWP_E_CALLOUT_NOTIFICATION_FAILED means that a callout’s notification routine returned an error while a filter referencing that callout was being added. The filter engine accepted neither a silent fallback nor a partially trusted callout state; the driver or component that owns the callout must provide the real reason.
What to collect
- Capture the callout key, layer, filter definition, notification operation, and the status returned by the callout routine.
- Inspect the callout driver’s event log or trace at the same time, including any initialization dependency such as provider context, configuration, or service state.
- Verify the documented order: register the callout with the filter engine, add the callout object to WFP, then add the filter that references it.
Do not weaken enforcement blindly
By default, filters that reference a callout added to WFP but not yet registered are treated as block filters. Replacing a failed callout rule with an unconditional permit changes the security contract; repair the callout registration and notification path instead.
Microsoft: WFP error codes · Microsoft: callout registration order and behavior · Microsoft: WFP callout role
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