hacktricks/pentesting/pentesting-web/403-and-401-bypasses.md

# 403 & 401 Bypasses

## HTTP Verbs/Methods Fuzzing

Try using **different verbs** to access the file: `GET, HEAD, POST, PUT, DELETE, CONNECT, OPTIONS, TRACE, PATCH, INVENTED, HACK`

* Check the response headers, maybe some information can be given. For example, a **200 response** to **HEAD** with `Content-Length: 55` means that the **HEAD verb can access the info**. But you still need to find a way to exfiltrate that info.
* Using a HTTP header like `X-HTTP-Method-Override: PUT` can overwrite the verb used.
* Use **`TRACE`** verb and if you are very lucky maybe in the response you can see also the **headers added by intermediate proxies** that might be useful.

## HTTP Headers Fuzzing

* **Change Host header** to some arbitrary value ([that worked here](https://medium.com/@sechunter/exploiting-admin-panel-like-a-boss-fc2dd2499d31))
* Try to [**use other User Agents**](https://github.com/danielmiessler/SecLists/blob/master/Fuzzing/User-Agents/UserAgents.fuzz.txt) to access the resource.
*   **Fuzz HTTP Headers**: Try using HTTP Proxy **Headers**, HTTP Authentication Basic and NTLM brute-force (with a few combinations only) and other techniques. To do all of this I have created the tool [**fuzzhttpbypass**](https://github.com/carlospolop/fuzzhttpbypass).

    * `X-Originating-IP: 127.0.0.1`
    * `X-Forwarded-For: 127.0.0.1`
    * `X-Forwarded: 127.0.0.1`
    * `Forwarded-For: 127.0.0.1`
    * `X-Remote-IP: 127.0.0.1`
    * `X-Remote-Addr: 127.0.0.1`
    * `X-ProxyUser-Ip: 127.0.0.1`
    * `X-Original-URL: 127.0.0.1`
    * `Client-IP: 127.0.0.1`
    * `True-Client-IP: 127.0.0.1`
    * `Cluster-Client-IP: 127.0.0.1`
    * `X-ProxyUser-Ip: 127.0.0.1`
    * `Host: localhost`

    If the **path is protected** you can try to bypass the path protection using these other headers:

    * `X-Original-URL: /admin/console`
    * `X-Rewrite-URL: /admin/console`
* If the page is **behind a proxy**, maybe it's the proxy the one preventing you you to access the private information. Try abusing [**HTTP Request Smuggling**](../../pentesting-web/http-request-smuggling/) **or** [**hop-by-hop headers**](../../pentesting-web/abusing-hop-by-hop-headers.md)**.**
* Fuzz [**special HTTP headers**](special-http-headers.md) looking for different response.
  * **Fuzz special HTTP headers** while fuzzing **HTTP Methods**.

## Path **Fuzzing**

If _/path_ is blocked:

* Try using _**/**_**%2e/path **_**(if the access is blocked by a proxy, this could bypass the protection). Try also**_** /%252e**/path (double URL encode)
* Try **Unicode bypass**: _/**%ef%bc%8f**path_ (The URL encoded chars are like "/") so when encoded back it will be _//path_ and maybe you will have already bypassed the _/path_ name check
* **Other path bypasses**:
  * site.com/secret –> HTTP 403 Forbidden
  * site.com/SECRET –> HTTP 200 OK
  * site.com/secret/ –> HTTP 200 OK
  * site.com/secret/. –> HTTP 200 OK
  * site.com//secret// –> HTTP 200 OK
  * site.com/./secret/.. –> HTTP 200 OK
  * site.com/;/secret –> HTTP 200 OK
  * site.com/.;/secret –> HTTP 200 OK
  * site.com//;//secret –> HTTP 200 OK
  * site.com/secret.json –> HTTP 200 OK (ruby)
  * Use all [**this list**](https://github.com/danielmiessler/SecLists/blob/master/Fuzzing/Unicode.txt) in the following situations:
    * /FUZZsecret
    * /FUZZ/secret
    * /secretFUZZ
* **Other API bypasses:**
  * /v3/users\_data/1234 --> 403 Forbidden
  * /v1/users\_data/1234 --> 200 OK
  * {“id”:111} --> 401 Unauthriozied
  * {“id”:\[111]} --> 200 OK
  * {“id”:111} --> 401 Unauthriozied
  * {“id”:{“id”:111\}} --> 200 OK
  * {"user\_id":"\<legit\_id>","user\_id":"\<victims\_id>"} (JSON Parameter Pollution)
  * user\_id=ATTACKER\_ID\&user\_id=VICTIM\_ID (Parameter Pollution)

## **Other Bypasses**

* Get the **IP** or **CNAME** of the domain and try **contacting it directly**.
* Try to **stress the server** sending common GET requests ([It worked for this guy wit Facebook](https://medium.com/@amineaboud/story-of-a-weird-vulnerability-i-found-on-facebook-fc0875eb5125)).
* **Change the protocol**: from http to https, or for https to http
* Go to [**https://archive.org/web/**](https://archive.org/web/) and check if in the past that file was **worldwide accessible**.

## **Brute Force**

* **Guess the password**: Test the following common credentials. Do you know something about the victim? Or the CTF challenge name?
*   [**Brute force**](../../brute-force.md#http-brute)**:** Try basic, digest and NTLM auth.

    {% code title="Common creds" %}
    ```
    admin    admin
    admin    password
    admin    1234
    admin    admin1234
    admin    123456
    root     toor
    test     test
    guest    guest
    ```
    {% endcode %}

## Automatic Tools

* [https://github.com/lobuhi/byp4xx](https://github.com/lobuhi/byp4xx)
* [https://github.com/iamj0ker/bypass-403](https://github.com/iamj0ker/bypass-403)
* [https://github.com/gotr00t0day/forbiddenpass](https://github.com/gotr00t0day/forbiddenpass)