Executive Summary

CVE-2026-3308 is an integer overflow vulnerability in Artifex's MuPDF version 1.27.0, specifically in the function that loads images from PDFs. The vulnerability occurs because the calculation of the number of bytes per source image line (src_stride) uses 32-bit integer arithmetic, which can overflow when multiplying the image width, bit depth, and number of components per pixel.

This overflow can cause incorrect memory operations, leading to a heap out-of-bounds write. An attacker can craft a malicious PDF that triggers this overflow, potentially allowing arbitrary code execution on the affected system.

The issue was fixed by changing the calculation to use 64-bit integer arithmetic, preventing the overflow.

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Impact Analysis

This vulnerability can allow an attacker to execute arbitrary code on your system by opening a specially crafted malicious PDF file. This could lead to unauthorized access, data theft, system compromise, or disruption of services.

Because the vulnerability involves a heap out-of-bounds write, it can be exploited to manipulate the program's behavior, potentially giving the attacker control over the affected application or the underlying system.

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Detection Guidance

This vulnerability is an integer overflow in the MuPDF library's image loading function. Detection involves identifying if your system is running a vulnerable version of MuPDF, specifically version 1.27.0 or earlier before the fix.

You can check the installed MuPDF version by running the following command on your system:

• mupdf --version

To detect attempts to exploit this vulnerability, monitor for suspicious PDF files that may trigger the integer overflow in the 'pdf_load_image_imp' function. However, no specific network detection commands or signatures are provided.

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Mitigation Strategies

The immediate mitigation step is to update MuPDF to a version that includes the fix for this vulnerability. The fix involves changing the integer arithmetic in the source code to use 64-bit integers to prevent overflow.

If you maintain the MuPDF source code, apply the patch that changes the calculation of 'src_stride' in the 'unpack_stream' function from 32-bit to 64-bit arithmetic as shown in the commit:

• int src_stride = ((int64_t) w * depth * n + 7) >> 3;

Alternatively, upgrade to the latest MuPDF version from the official repository where this fix is included.

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Compliance Impact

The provided information does not specify how the integer overflow vulnerability in MuPDF version 1.27.0 impacts compliance with common standards and regulations such as GDPR or HIPAA.

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