Artifex Ghostscript is a widely used software suite that offers a wide range of operations on PostScript, PDF, and other document formats. With its high interoperability, Ghostscript is integrated into numerous applications and platforms such as operating systems, web servers, and imaging applications.

A vulnerability has been discovered in Artifex Ghostscript versions earlier than 10.03.1, allowing an attacker to cause memory corruption and bypass the SAFER sandbox security feature. This vulnerability is mainly caused by format string injection when using a uniprint device.

About the Vulnerability: CVE-2024-29510

The vulnerability (CVE-2024-29510) arises from the implementation of the uniprint functionality in Ghostscript. By exploiting this vulnerability, an attacker can trigger memory corruption and bypass the SAFER sandbox protection mechanism, which is used to restrict malicious PostScript code execution.

The exploit takes advantage of the way process_formatted() function handles user input, which does not properly validate format strings. This allows an attacker to inject malicious code into the format string and cause memory corruption or arbitrary code execution.

Exploiting the Vulnerability

To exploit this vulnerability, the attacker must create a specially crafted PostScript file containing malicious format strings and execute this file via Ghostscript with the uniprint device in use. The code snippet below demonstrates how an attacker could create a malicious PostScript file to exploit the vulnerability:

%!PS
/save restore def
/SAFER{ (Exploiting...) = } def
/uniprint {
    % Custom uniprint device
    /device 5 dict dup begin
        /PrintCommands true
        /Initialize { % vulnerable function
            process_formatted(alert.begin)
        } def
    end
} bind def

/alert 260 string def
(%%.\00200x%10$s) alert sprintf      % Injecting format string into the alert buffer
uniprint setdevice

This malicious PostScript file injects a format string "%10$s" into the alert buffer. When the process_formatted() function is called during the Initialize procedure, the injected format string overwrites memory structures and bypasses the SAFER sandbox mechanism causing the "Exploiting..." message to be displayed.

Mitigation and Remedy

Artifex has released a security patch for Ghostscript to address this vulnerability in releases greater than or equal to 10.03.1. Users are strongly encouraged to upgrade their Ghostscript installations to a version containing the fix.

To further protect your system against any potential Ghostscript-related vulnerabilities, it is a good practice to:

Update your system software periodically and make sure to apply security patches.

- Run your applications and services with the least necessary privilege; avoid running as a root user or administrator when not needed.

- Restrict the use of potentially harmful Ghostscript features, such as file operations or external command execution in your application configuration.

- Implement strict user input validation and filtering mechanisms to avoid allowing malicious code injection.

Original References

- Artifex Ghostscript Website: http://www.ghostscript.com

- CVE Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-29510

- Artifex Ghostscript Patches: https://www.ghostscript.com/doc/current/Patches.htm

Conclusion

CVE-2024-29510 is a critical security vulnerability affecting Artifex Ghostscript versions before 10.03.1. The vulnerability involves memory corruption and SAFER sandbox bypass, which are caused by format string injection with a uniprint device. The attacker can create a specially crafted PostScript file containing malicious format strings to exploit the vulnerability.

The vulnerability can be mitigated easily by upgrading Ghostscript to a version greater than or equal to 10.03.1. It is important to stay vigilant and apply best practices to increase the overall security posture of your systems.

Timeline

Published on: 07/03/2024 19:15:03 UTC
Last modified on: 07/30/2024 03:55:31 UTC