CVE-2025-69725: Github.com/go chi/chi/v5 Chi Has An Open Redirect Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-mqqf-5wvp-8fh8",
  "modified" : "2026-06-18T13:02:20Z",
  "published" : "2026-01-14T21:18:06Z",
  "aliases" : [ "CVE-2025-69725" ],
  "summary" : "chi has an open redirect vulnerability in the RedirectSlashes middleware",
  "details" : "### Summary\n\nThe `RedirectSlashes` function in middleware/strip.go does not perform correct input validation and can lead to an open redirect vulnerability.\n\n### Details\n\nThe `RedirectSlashes` function performs a `Trim` to all forward slash (`/`) characters, while prepending a single one at the begining of the path (Line 52).\n\nHowever, it does not trim backslashes (`\\`).\n\n```go\nFile: middleware/strip.go\n41: func RedirectSlashes(next http.Handler) http.Handler {\n...\n51: \t\t\t// Trim all leading and trailing slashes (e.g., \"//evil.com\", \"/some/path//\")\n52: \t\t\tpath = \"/\" + strings.Trim(path, \"/\")\n...\n62: }\n```\n\nAlso, 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](https://github.com/go-chi/chi/security/advisories/GHSA-vrw8-fxc6-2r93)](https://github.com/go-chi/chi/security/advisories/GHSA-vrw8-fxc6-2r93).\n\nThe above make it possible for a response in the following form:\n\n```\nHTTP/1.1 301 Moved Permanently\nLocation: /\\evil.com\n```\n\nThe `/\\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.\n\n### PoC\n\nA minimal working example can be seen below.\n\n```go\npackage main\n\nimport (\n\t\"fmt\"\n\t\"net/http\"\n\n\t\"github.com/go-chi/chi/v5\"\n\t\"github.com/go-chi/chi/v5/middleware\"\n)\n\n\n\nfunc main() {\n\tr := chi.NewRouter()\n\n\tr.Use(middleware.RedirectSlashes)\n\n\tr.Get(\"/*\", func(w http.ResponseWriter, r *http.Request) {\n\t\tw.WriteHeader(http.StatusOK)\n\t})\n\n\tfmt.Println(\"Server starting on port 8081...\")\n\tif err := http.ListenAndServe(\":8081\", r); err != nil {\n\t\tfmt.Printf(\"Error starting server: %v\\n\", err)\n\t}\n}\n\n```\n\nAnd 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.\n\n```bash\n$ curl -I  localhost:8081/\\\\evil.com/\nHTTP/1.1 301 Moved Permanently\nContent-Type: text/html; charset=utf-8\nLocation: /\\evil.com\n```\n\n```bash\n$ curl -I  localhost:8081/%5Cevil.com/\nHTTP/1.1 301 Moved Permanently\nContent-Type: text/html; charset=utf-8\nLocation: /\\evil.com\n```\n\nThis 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`.\n<img width=\"200\" alt=\"image-20250829115619807\" src=\"https://github.com/user-attachments/assets/44aedad1-64b6-4660-8b26-fad9b4eca036\" />\n\n\n<img width=\"200\" alt=\"image-20250829115632067\" src=\"https://github.com/user-attachments/assets/b976d47d-1975-469c-abd3-deb907a68db2\" />\n\n\n### Impact\n\nThis 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).\n\nThe 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.\n\nThis 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.\n\nIn order to exploit this vulnerability the attacker does not need to be authenticated or have ay other priviledge / knowledge regarding the affected application.\n\nCVSS Score: [4.7 (Medium)](https://www.first.org/cvss/calculator/3-0#CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/go-chi/chi/v5"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "5.2.2"
      }, {
        "fixed" : "5.2.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/go-chi/chi/security/advisories/GHSA-mqqf-5wvp-8fh8"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-69725"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-chi/chi/issues/1037"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/go-chi/chi/commit/6eb35881c0e438ffb663ddbad3a61babaa5e5d8a"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/go-chi/chi"
  }, {
    "type" : "WEB",
    "url" : "http://go-chichi.com"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-601" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-01-14T21:18:06Z",
    "nvd_published_at" : null
  }
}