Heartbleed in Chi

Chi (github.com/go-chi/chi/v5) is a lightweight HTTP router for Go. It does not implement TLS itself; security of the transport layer depends on the net/http server and the underlying TLS stack. When a Go program is built with CGO enabled and links against an older version of OpenSSL (prior to 1.0.1g), the crypto/tls package may delegate to that OpenSSL library. In that scenario, the Heartbleed bug (CVE-2014-0160) can be triggered: a malformed TLS heartbeat request causes the server to return up to 64 KB of its process memory, potentially exposing private keys, session tokens, or other sensitive data handled by your Chi‑based API.

Because Chi only defines request handlers, the vulnerability appears in the bootstrap code where the server is started. A typical Chi application looks like this:

package main

import (
	"net/http"
	"github.com/go-chi/chi/v5"
)

func main() {
	r := chi.NewRouter()
	r.Get("/", func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte("OK"))
	})

	// ListenAndServeTLS uses the Go TLS stack
	http.ListenAndServeTLS(":443", "cert.pem", "key.pem", r)
}

If the binary was built with CGO_ENABLED=1 and the system’s OpenSSL is vulnerable, the ListenAndServeTLS call will use that vulnerable library, making the Heartbleed exposure possible even though the Chi router itself is unaffected.

middleBrick’s encryption check includes an active Heartbleed test. When you submit an HTTPS URL, the scanner sends a crafted TLS heartbeat payload and analyses the response. If the server returns more data than the payload length, the finding is flagged under the Encryption category with a reference to CVE‑2014-0160.

You can run this check from the command line using the middleBrick CLI:

middlebrick scan https://api.example.com

The tool returns a JSON report. A relevant excerpt might look like:

{
  "category": "Encryption",
  "findings": [
    {
      "id": "ENC-HEARTBLEED",
      "severity": "high",
      "title": "Potential Heartbleed vulnerability (CVE-2014-0160)",
      "description": "The server responded with excess data to a TLS heartbeat request, indicating a vulnerable OpenSSL version.",
      "remediation": "Upgrade OpenSSL to ≥1.0.1g or rebuild the Go binary with CGO_DISABLED=1 to use Go’s native TLS implementation."
    }
  ]
}

Because middleBrick requires no agents, credentials, or configuration, you can integrate this scan into your CI pipeline (e.g., via the GitHub Action) to catch the issue before deploying a Chi‑based service.

The most reliable fix is to ensure your Go binary does not depend on a vulnerable OpenSSL library. Go’s standard crypto/tls package provides a pure‑Go TLS implementation that is not affected by Heartbleed. To use it, either:

• Build with CGO disabled: CGO_ENABLED=0 go build -o myservice .
• Upgrade the system OpenSSL to version 1.0.1g or newer if you must keep CGO enabled.

After rebuilding, verify that the binary no longer links to OpenSSL (on Linux, ldd myservice | grep ssl should show no matches). Then restart your Chi service.

Example of a safe build and run:

# Disable CGO and build
CGO_ENABLED=0 go build -o api-service .

# Run the service (TLS uses Go’s native stack)
./api-service

If you explicitly configure a custom tls.Config (for instance, to load certificates from HashiCorp Vault), make sure you do not set Config.Rand to an OpenSSL‑dependent source. The default crypto/rand.Reader is safe.

Finally, because Heartbleed could have leaked private keys, replace any TLS certificates and keys that were in use while the vulnerable version was running, even after patching.