CVE-2017-5991 in MuPDF
Summary
by MITRE
An issue was discovered in Artifex Software, Inc. MuPDF before 1912de5f08e90af1d9d0a9791f58ba3afdb9d465. The pdf_run_xobject function in pdf-op-run.c encounters a NULL pointer dereference during a Fitz fz_paint_pixmap_with_mask painting operation.
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Analysis
by VulDB Data Team • 11/30/2024
The vulnerability identified as CVE-2017-5991 represents a critical NULL pointer dereference flaw within the MuPDF document processing library developed by Artifex Software Inc. This issue exists in versions prior to the commit hash 1912de5f08e90af1d9d0a9791f58ba3afdb9d465, making it a significant concern for systems that rely on MuPDF for PDF rendering and processing operations. The flaw manifests specifically within the pdf_run_xobject function located in the pdf-op-run.c source file, which is responsible for executing xobject operations during PDF processing. This function interacts with the Fitz graphics library's fz_paint_pixmap_with_mask painting operation, creating a chain of execution that ultimately leads to the exploitable condition.
The technical nature of this vulnerability stems from inadequate input validation and null pointer checking within the PDF parsing and rendering pipeline. When MuPDF processes certain malformed or specially crafted PDF documents, the pdf_run_xobject function fails to properly validate pointer references before dereferencing them during the painting operation. This NULL pointer dereference occurs during the execution of the fz_paint_pixmap_with_mask function, which is part of the Fitz graphics rendering engine that handles pixmap operations with masking capabilities. The flaw essentially allows an attacker to craft a PDF file that, when processed by vulnerable MuPDF implementations, will cause the application to crash or potentially execute arbitrary code through memory corruption.
From an operational impact perspective, this vulnerability presents a substantial risk to organizations that utilize MuPDF in their document processing workflows, particularly those that handle untrusted PDF files from external sources. The NULL pointer dereference can lead to denial of service conditions where applications crash and become unavailable to legitimate users, disrupting business operations and potentially enabling attackers to perform persistent denial of service attacks. In more severe scenarios, if the memory corruption is properly exploited, it could potentially allow for arbitrary code execution, though the specific exploitability of this particular flaw would depend on additional factors including memory layout and system protections. The vulnerability affects not only standalone applications but also web services, mobile applications, and enterprise systems that incorporate MuPDF as a core component for PDF handling.
Mitigation strategies for CVE-2017-5991 should prioritize immediate patching of all affected MuPDF installations to versions containing the fix referenced in the commit 1912de5f08e90af1d9d0a9791f58ba3afdb9d465. Organizations should also implement comprehensive input validation and sanitization measures for all PDF files processed through their systems, including deploying sandboxing techniques and content filtering mechanisms. Network-level protections such as web application firewalls and PDF content inspection tools can help detect and block malicious PDF files before they reach vulnerable applications. Additionally, system hardening measures including stack canaries, address space layout randomization, and other exploit mitigations should be implemented to reduce the potential impact if exploitation were to occur. This vulnerability aligns with CWE-476, which specifically addresses NULL pointer dereference conditions, and could potentially map to ATT&CK techniques involving privilege escalation and code execution through software exploitation. Regular security assessments and vulnerability scanning should be conducted to ensure all systems utilizing MuPDF remain protected against similar issues.