CVE-2017-7264 in MuPDF
Summary
by MITRE
Use-after-free vulnerability in the fz_subsample_pixmap function in fitz/pixmap.c in Artifex Software, Inc. MuPDF 1.10a allows remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact via a crafted document.
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Analysis
by VulDB Data Team • 08/24/2025
The CVE-2017-7264 vulnerability represents a critical use-after-free flaw within the MuPDF document processing library, specifically within the fz_subsample_pixmap function located in fitz/pixmap.c. This vulnerability affects Artifex Software, Inc. MuPDF version 1.10a and presents a significant security risk to systems that process untrusted PDF documents. The flaw manifests when the application encounters specially crafted malicious documents that trigger improper memory management during pixmap subsampling operations. The vulnerability falls under the CWE-416 category of Use After Free, which occurs when a program continues to reference memory after it has been freed, leading to unpredictable behavior and potential exploitation. This particular implementation flaw demonstrates a classic memory safety issue where the fz_subsample_pixmap function fails to properly validate or manage memory references during the subsampling process of pixmap objects.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable more severe consequences including arbitrary code execution or complete system compromise. When a remote attacker crafts a malicious PDF document containing malformed pixmap data, the vulnerable MuPDF library will attempt to process this data through the flawed fz_subsample_pixmap function. The use-after-free condition occurs during the memory deallocation and subsequent reuse phases, where the application may attempt to access freed memory locations that have already been returned to the system heap. This behavior can result in application crashes, memory corruption, or potentially enable attackers to execute malicious code within the context of the vulnerable application. The vulnerability's remote exploitability means that attackers can leverage this flaw without requiring local access to the target system, making it particularly dangerous in web-based environments where PDF documents are commonly processed.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1203 - Exploitation for Client Execution, where attackers leverage application vulnerabilities to execute code remotely. The vulnerability demonstrates a failure in proper input validation and memory management within the document rendering pipeline, creating an attack surface that can be exploited through document processing. The affected MuPDF library is widely deployed across various applications including web browsers, document viewers, and enterprise document management systems, amplifying the potential impact of this vulnerability. Security researchers have identified that the flaw occurs during the pixmap subsampling operation where the application attempts to reduce the resolution of pixmap data, but fails to properly handle memory references when processing malformed input data. The vulnerability's classification as a remote attack vector means that exploitation can occur through web browsers, email clients, or any application that processes PDF documents without proper input sanitization.
Mitigation strategies for CVE-2017-7264 should prioritize immediate patching of affected systems with the latest MuPDF releases that contain memory safety fixes. Organizations should implement comprehensive input validation and sanitization measures for all PDF document processing workflows, particularly in web-facing applications. The implementation of memory safety controls including address space layout randomization, stack canaries, and heap metadata validation can provide additional defense-in-depth measures. Network segmentation and application whitelisting can help limit the attack surface by restricting which systems can process untrusted PDF content. Security monitoring should focus on detecting unusual application behavior, memory access patterns, and potential exploitation attempts through network traffic analysis. Regular security assessments and vulnerability scanning should be conducted to identify other potential memory safety issues within document processing libraries. System administrators should also consider implementing sandboxing mechanisms for PDF processing applications to contain potential exploitation attempts and limit the impact of successful attacks. The vulnerability highlights the importance of regular security updates and proper memory management practices in document rendering libraries, particularly those handling untrusted input data.