What causes "Could not get underlying FeroxScans" in epi052/feroxbuster?

Initialize FeroxScans on the container before querying it

Could not get underlying FeroxScans

Error message

Could not get underlying FeroxScans

What it means

ferox_scans returns this error when the FeroxScans handle behind the container's RwLock cannot be read or is None. Callers use this to get scan data (e.g. collected_extensions); without the handle, scan bookkeeping is unavailable.

Solutions

Initialize FeroxScans on the container before querying it
Recover or replace a poisoned lock (check for an earlier panic that poisoned scans)
Call ferox_scans only after the scan event loop has started
In tests, use the standard container constructor instead of a partial default

Example fix

// before
let scans = container.ferox_scans()?; // before init
// after
container.initialize()?;
let scans = container.ferox_scans()?;

Defensive patterns

Strategy: try-catch

Validate before calling

if container.scans_initialized() {
    let scans = container.ferox_scans()?;
}

Try / catch

let scans = match container.ferox_scans() {
    Ok(s) => s,
    Err(e) if e.to_string().contains("Could not get underlying FeroxScans") => {
        log::warn!("FeroxScans not initialized yet");
        return Ok(());
    }
    Err(e) => return Err(e),
};

Prevention

Initialize FeroxScans before querying scan metadata
Avoid accessing scan state from threads that may panic (poisons the lock)
Query scan data only while the scan event loop is running

When it happens

Trigger: Calling ferox_scans when self.scans holds None (container created without FeroxScans initialized) or the RwLock read fails due to poisoning after a panic elsewhere.

Common situations: Accessing scan metadata before the scan handler initialized FeroxScans; use in tests with a manually-built container; a poisoned lock after a panic in a scan task.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of epi052/feroxbuster@1f595dab5c (2026-09-13). Data as JSON: /api/errors/bc1a8a8212f9b854. Report an issue: GitHub.

Appendix: source

Thrown at src/event_handlers/container.rs:181

        let methods = self.config.methods.len().max(1);
        let base_requests = 1; // the bare word (with optional slash)
        let static_extensions = self.config.extensions.len();
        let dynamic_extensions = self.num_collected_extensions();

        let total_paths = base_requests + static_extensions + dynamic_extensions;

        total_paths * methods
    }

    /// Helper to easily get the (locked) underlying FeroxScans object
    pub fn ferox_scans(&self) -> Result<Arc<FeroxScans>> {
        if let Ok(guard) = self.scans.read().as_ref() {
            if let Some(handle) = guard.as_ref() {
                return Ok(handle.data.clone());
            }
        }

        bail!("Could not get underlying FeroxScans")
    }
}

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