CVE-2023-28879 - Exploring Artifex Ghostscript Buffer Overflow Vulnerability

In Artifex Ghostscript, a popular suite of software for working with PostScript and PDF files, a recently discovered buffer overflow vulnerability has been spotted in versions up to 10.01.. The vulnerability, dubbed as CVE-2023-28879, affects the functions BCPEncode, BCPDecode, TBCPEncode, and TBCPDecode in the base/sbcp.c file of the codebase. In this long read, we will dive into the details of this issue, explore the code snippets, and provide references and links to original sources.

Exploit Details

The buffer overflow vulnerability occurs when the write buffer is nearly full, specifically when there's only one byte left, and a user attempts to write an escaped character. In this scenario, the system writes two bytes instead of one, leading to potential data corruption inside the PostScript interpreter.

Here's a code snippet showcasing the vulnerability

// sbcp.c
case S:
    if (count == max_count) {
        StreamEncodeStatus status = s_BCPE_template.process(s, NULL, , true);

        if (status < )
            return status;
        count = ;
    }
    p[count++] = c; // <- Buffer Overflow Vulnerability
}

In this code, if max_count is equal to capacity - 1, the buffer overflows when c contains an escaped character which requires two bytes to be written.

Potential Impact

A successful exploitation of this vulnerability could lead to data corruption in the PostScript interpreter, resulting in a crash or incorrect rendering. In a worst-case scenario, an attacker might be able to execute arbitrary code, potentially compromising the system.

Mitigations

As of the time of writing, Artifex has not yet released an official patch for this vulnerability. It is recommended to check with the vendor regularly for updates and use the latest available version of the software. Furthermore, users should be cautious when working with untrusted PostScript files.

Here are some links to the original sources and related pieces of information

- CVE-2023-28879 Vulnerability Detailed Report
- Artifex Ghostscript Official Homepage
- Artifex Ghostscript Source Code Repository
- base/sbcp.c in Ghostscript Source Code Repository

Conclusion

CVE-2023-28879 is a significant buffer overflow vulnerability discovered in Artifex Ghostscript, a widely used software suite for handling PostScript and PDF files. This vulnerability has the potential to cause data corruption inside the PostScript interpreter and, in some cases, might even lead to system compromise. It is crucial for users to stay up-to-date with software updates from the vendor and remain cautious when dealing with untrusted PostScript files.

Timeline

Published on: 03/31/2023 17:15:00 UTC
Last modified on: 04/15/2023 04:16:00 UTC