Double Free in Echo Go with Basic Auth

A Double Free vulnerability occurs when a program deallocates the same memory region twice. In Go, this is less common due to garbage collection, but it can surface in HTTP handlers when unsafe interactions between the request context, authentication parsing, and response handling cause underlying resources to be released more than once. When Basic Authentication is used in an Echo Go application, the framework parses the Authorization header on every request. If the handler logic or middleware retains references to parsed credentials and also manipulates response writers or context objects in a way that triggers multiple flushes or closures, the interplay can expose use-after-free-like behavior in the surrounding runtime or native libraries that Echo depends on.

Consider an Echo route configured with Basic Auth parsing and a custom middleware that inspects credentials. If the middleware stores a pointer to the parsed username or password and the handler later modifies or releases associated objects (for example, by reusing a context value or closing a response body prematurely), the same memory can be freed when the request context completes and when the garbage collector or HTTP server finalizes the response. This specific combination—Echo’s routing, Basic Auth header extraction, and aggressive response handling—can amplify risks when developers inadvertently retain references or call write operations after the response is considered complete.

Real-world patterns that can contribute include attaching parsed auth values to the context and then mutating them in downstream handlers, or using response writers in multiple middleware layers without guarding against repeated writes. An attacker could send crafted requests that cause the server to process the same credential object in multiple phases, potentially leading to crashes or information leakage through timing or error paths. While Go’s runtime prevents direct memory corruption in many cases, the interaction between Echo’s lifecycle, Basic Auth parsing, and developer code can still lead to unstable states that resemble Double Free conditions in native code.

From a scanning perspective, tools like middleBrick examine the unauthenticated attack surface and check for indicators such as missing input validation around authentication headers, inconsistent use of context values, and patterns where response writers are accessed after closure. The LLM/AI Security checks can additionally probe whether prompt or configuration leakage could occur if error messages reveal stack traces or environment details when such invalid states are triggered. Findings typically highlight the need to ensure that authentication-derived data is not shared across goroutines without proper synchronization and that response lifecycle methods are called exactly once per request.

To mitigate Double Free risks and related instability in Echo Go with Basic Authentication, adopt patterns that avoid retaining or mutating parsed credentials beyond the immediate handler and ensure response writers are used safely. Always parse credentials within the handler or a tightly scoped middleware, and avoid attaching them to the request context for later use. Validate and sanitize the username and password immediately, and do not reuse objects across multiple middleware layers or handler invocations.

Below is a secure example of Basic Auth in Echo Go that avoids problematic patterns. The credentials are verified once, used only to authorize the request, and not stored in context for reuse.

package main

import (
    "net/http"
    "strings"

    "github.com/labstack/echo/v4"
)

// authenticate extracts and validates Basic Auth credentials for a single request.
func authenticate(next echo.HandlerFunc) echo.HandlerFunc {
    return func(c echo.Context) error {
        user, pass, ok := c.Request().BasicAuth()
        if !ok || !isValidUser(user, pass) {
            return echo.ErrUnauthorized
        }
        // Do NOT store user/pass in c.Set for later handlers.
        return next(c)
    }
}

func isValidUser(username, password string) bool {
    // Replace with secure credential validation (e.g., constant-time compare).
    return username == "admin" && password == "securepass"
}

func main() {
    e := echo.New()

    e.GET/protected", authenticate(func(c echo.Context) error {
        // Handler logic that does not reuse or mutate auth objects.
        return c.String(http.StatusOK, "Authenticated access")
    }))

    e.Logger.Fatal(e.Start(":8080"))
}

Avoid the anti-pattern below, where parsed credentials are attached to the context and later reused, increasing the risk of unsafe interactions across middleware or handlers.

// Anti-pattern: attaching parsed credentials to context.
func insecureMiddleware(next echo.HandlerFunc) echo.HandlerFunc {
    return func(c echo.Context) error {
        user, pass, ok := c.Request().BasicAuth()
        if ok && isValidUser(user, pass) {
            c.Set("username", user) // Risk of unsafe sharing.
            c.Set("password", pass)
        }
        return next(c)
    }
}

Additional remediation steps include ensuring that custom middleware does not call response writer methods after the response has been committed and that errors from authentication checks do not leak sensitive information in headers or bodies. middleBrick’s scans can help identify routes where authentication parsing is inconsistent or where context values are improperly propagated. With the Pro plan, continuous monitoring can alert you if new endpoints introduce patterns that resemble Double Free conditions or other memory-related anomalies, while the CLI allows you to validate fixes locally before deploying changes.