Fix stack trace leaked in error response in Koa

Returning an error's `.stack` to the client exposes absolute file paths, dependency versions, and internal call structure. Attackers use it to map the application and to fingerprint vulnerable dependency versions. Log the stack server-side and return a generic message.

high likely Koa CWE-209 / OWASP A05:2021

The vulnerable pattern in Koa

This finding comes from the Koa fixture in the owlwarden test suite. Stack traces expose absolute file paths, dependency versions, and internal call structure - enough to fingerprint the stack and locate other weaknesses.

The corrected handler

Log server-side and send a generic body.

console.error(err)
ctx.status = 500
ctx.body = { error: 'Internal Server Error' }

If you are not using Koa

Log the error server-side and return a generic message to the client.

Check your own repository

npx owlwarden scan
npx owlwarden explain stack-trace-leak

Runs on your machine. No account, no telemetry, no network unless you ask. In CI, SARIF uploads to code scanning and the exit code is the gate.

Other Koa checks

Rules with a tested Koa example.

• cors-permissive medium Cross-origin policy accepts any origin
• hardcoded-secret high Credential hardcoded in source
• insecure-cookie medium Cookie set without its protective attributes
• install-lifecycle-script medium Package declares an install-time script
• open-redirect medium Redirect target comes from the caller
• security-headers-missing medium Security headers are not configured
• sensitive-data-logged medium Sensitive data written to a log
• sql-injection high SQL query built by string interpolation
• ssrf high Server fetches a URL the caller controls
• weak-crypto high Broken cryptographic primitive protecting a secret

stack-trace-leak for every framework / All rules / owlwarden