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Host Header Injection Leads to Open Redirect in RedirectSlashes
Description
Summary
The RedirectSlashes function in middleware/strip.go is vulnerable to host header injection which leads to open redirect.
We consider this alower-severity open redirect, as it can't be exploited from browsers or email clients (requires manipulation of a Host header).
Details
The RedirectSlashes method uses the Host header to construct the redirectURL at this linehttps://github.com/go-chi/chi/blob/master/middleware/strip.go#L55
The Host header can be manipulated by a user to be any arbitrary host. This leads to open redirect when using the RedirectSlashes middleware
PoC
Create a simple server which uses the RedirectSlashes middleware
package mainimport ("fmt""net/http""github.com/go-chi/chi/v5""github.com/go-chi/chi/v5/middleware" // Import the middleware package)func main() {// Create a new Chi routerr := chi.NewRouter()// Use the built-in RedirectSlashes middlewarer.Use(middleware.RedirectSlashes) // Use middleware.RedirectSlashes// Define a route handlerr.Get("/", func(w http.ResponseWriter, r *http.Request) {// A simple responsew.Write([]byte("Hello, World!"))})// Start the serverfmt.Println("Starting server on :8080")http.ListenAndServe(":8080", r)}Run the servergo run main.go
Once the server is running, send a request that will trigger the RedirectSlashes function with an arbitrary Host headercurl -iL -H "Host: example.com" http://localhost:8080/test/
Observe that the request will be redirected to example.com
curl -L -H "Host: example.com" http://localhost:8080/test/<!doctype html><html><head> <title>Example Domain</title> <meta charset="utf-8" /> <meta http-equiv="Content-type" content="text/html; charset=utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1" /> <style type="text/css"> body { background-color: #f0f0f2; margin: 0; padding: 0; font-family: -apple-system, system-ui, BlinkMacSystemFont, "Segoe UI", "Open Sans", "Helvetica Neue", Helvetica, Arial, sans-serif;... snipped ...Without the host header, the response is returned from the test server
curl -L http://localhost:8080/test/404 page not foundImpact
An open redirect vulnerability allows attackers to trick users into visiting malicious sites. This can lead to phishing attacks, credential theft, and malware distribution, as users trust the application’s domain while being redirected to harmful sites.
Potential mitigation
It seems that the purpose of the RedirectSlashes function is to redirect within the same application. In that case r.RequestURI can be used instead of r.Host by default. If there is a use case to redirect to a different host, a flag can be added to use the Host header instead. As this flag will be controlled by the developer they will make the decision of allowing redirects to arbitrary hosts based on their judgement.
Severity
CVSS v4 base metrics
Exploitability Metrics
Vulnerable System Impact Metrics
Subsequent System Impact Metrics
CVE ID
Weaknesses
WeaknessCWE-601
URL Redirection to Untrusted Site ('Open Redirect')
A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks.Learn more on MITRE.Credits
anuraagbaishyaReporter