Integer Overflow in Artifex Ghostscript Leading to DoS

Executive Summary

This vulnerability is an integer overflow in the function jbig2_arith_iaid_ctx_new() within the Artifex software. An integer overflow occurs when a calculation exceeds the maximum size that can be stored in an integer variable, potentially causing unexpected behavior.

In this case, the overflow can be triggered by a specially crafted input, which can lead to a Denial of Service (DoS) condition.

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Impact Analysis

The primary impact of this vulnerability is a Denial of Service (DoS). This means that an attacker could exploit the integer overflow by providing crafted input to the affected function, causing the software to crash or become unresponsive.

Such a DoS could disrupt normal operations of systems relying on the vulnerable Artifex component, potentially leading to downtime or service interruptions.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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Detection Guidance

This vulnerability can be detected by identifying if your system processes JBIG2 image files using a vulnerable version of the jbig2dec library, specifically versions prior to commit cc37d0931aa71582f7128736a068c92cd8712d9b.

To check if the vulnerable jbig2dec library is present, you can verify the version or commit of the jbig2dec installation on your system.

Since the vulnerability is triggered by crafted JBIG2 image files, monitoring for unusual crashes or Denial of Service (DoS) events in applications that process JBIG2 images (such as MuPDF) can also indicate exploitation attempts.

Suggested commands include:

• Check jbig2dec version or commit: If you have the source or binary, identify the version or commit hash to confirm if it is before cc37d0931aa71582f7128736a068c92cd8712d9b.
• Use the jbig2dec command line tool to test suspicious JBIG2 files: `jbig2dec suspicious_file.jb2` and observe if it crashes or behaves abnormally.
• Monitor application logs (e.g., MuPDF) for crashes or DoS symptoms when processing JBIG2 images.

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Mitigation Strategies

Immediate mitigation steps include:

• Update the jbig2dec library to a version that includes the fix after commit cc37d0 (i.e., at or after commit cc37d0931aa71582f7128736a068c92cd8712d9b).
• If updating is not immediately possible, avoid processing untrusted or suspicious JBIG2 image files that could trigger the integer overflow.
• Monitor applications that use jbig2dec (such as MuPDF) for crashes or Denial of Service symptoms and restrict access to these services if necessary.
• Report any suspicious activity or crashes to your security team and consider applying additional network-level protections to block malicious JBIG2 files.

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