CVE-2023-23403: Microsoft PostScript and PCL6 Class Printer Driver Remote Code Execution Vulnerability Explained

In a recent security bulletin (CVE-2023-23403), Microsoft released information on a critical vulnerability affecting the Microsoft PostScript and PCL6 Class Printer drivers. This vulnerability has the potential to allow remote code execution by an attacker, making it a significant risk to any organization that uses these drivers. In this blog post, we will dive into the details of this vulnerability, how it can be exploited, and what you can do to help mitigate the risk.

Overview

The Microsoft PostScript and PCL6 Class Printer drivers are used widely in many organizations for printing documents. These drivers are responsible for converting the Windows-based print jobs into a language that the printer can understand, either PostScript or PCL6.

The vulnerability in question (CVE-2023-23403) affects a specific function in these drivers, which can be exploited by an attacker who can send a specially crafted malicious file to be printed on the target system. When processed, this file can lead to a buffer overflow and allow the attacker to execute arbitrary code on the targeted machine.

Exploit Details

The vulnerability exists in the handling of certain data structures by the affected drivers, leading to a classic buffer overflow scenario. Without diving too deep into the technical details, here is a high-level overview of the exploit process:

The target user prints the file using the vulnerable PostScript or PCL6 Class Printer driver.

4. When the driver processes the malicious file, a buffer overflow occurs, allowing the attacker's code to be executed.

Here is a code snippet demonstrating the buffer overflow

// Buffer overflow example in the printer driver
void vulnerable_function(char *data) {
    char buffer[1024];    // Buffer of 1024 bytes
    strcpy(buffer, data); // Copies content from the data pointer into the buffer.
}

void main() {
    char large_data[2048]; // Large data to overflow the buffer
    memset(large_data, 'A', sizeof(large_data) - 1); // Fill large_data with 'A's
    vulnerable_function(large_data); // Pass the large_data to the function
}

In the above example, the vulnerable_function is part of the affected printer driver and can be exploited with a buffer overflow. By sending a large amount of data, in this case, 2048 bytes, the attacker can cause the buffer to overflow, potentially leading to arbitrary code execution.

Original References

Microsoft has acknowledged this vulnerability and provided a security bulletin with further details and suggested mitigations:

- Microsoft Security Bulletin: CVE-2023-23403
- Common Vulnerabilities and Exposures (CVE) Reference

To help mitigate the risk of this vulnerability, Microsoft has recommended the following steps

1. Apply the latest security patches for the affected Microsoft PostScript and PCL6 Class Printer drivers. This will fix the vulnerability and prevent the buffer overflow from occurring.
2. Ensure that your organization has a robust patch management program in place to keep all software up to date and protected against known vulnerabilities.
3. Educate users about the risks of opening files from unknown or suspicious sources, and implement security policies that restrict users from printing files that have not been adequately vetted.

Conclusion

CVE-2023-23403 is a critical vulnerability affecting the widely used Microsoft PostScript and PCL6 Class Printer drivers. It allows an attacker to remotely execute code on a target system, making it a significant risk to all organizations that use these drivers. It's crucial to apply the necessary security patches as soon as possible and follow Microsoft's recommendations to mitigate the risk. By following best practices for patch management and user education, you can help minimize the impact of this and other vulnerabilities in your organization.

Timeline

Published on: 03/14/2023 17:15:00 UTC
Last modified on: 03/23/2023 16:54:00 UTC