CVE-2017-17866 in MuPDF
Summary
by MITRE
pdf/pdf-write.c in Artifex MuPDF before 1.12.0 mishandles certain length changes when a repair operation occurs during a clean operation, which allows remote attackers to cause a denial of service (buffer overflow and application crash) or possibly have unspecified other impact via a crafted PDF document.
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Analysis
by VulDB Data Team • 01/19/2023
The vulnerability identified as CVE-2017-17866 resides within the pdf/pdf-write.c component of Artifex MuPDF library versions prior to 1.12.0. This issue manifests during the processing of PDF documents when the library performs repair operations alongside clean operations, creating a scenario where length changes in certain PDF structures are not properly handled. The flaw represents a classic buffer management error that can be exploited through maliciously crafted PDF files, making it particularly dangerous in environments where users might encounter untrusted document content. The vulnerability is categorized under CWE-121 as a stack-based buffer overflow, which occurs when data is written beyond the bounds of a allocated buffer, potentially leading to memory corruption.
The technical implementation of this vulnerability involves the pdf-write.c module's handling of PDF object structures during document repair processes. When MuPDF encounters a corrupted or malformed PDF document that requires cleaning, the repair operation attempts to adjust object lengths and structures. However, the code fails to properly validate or adjust buffer boundaries when these length changes occur, leading to situations where subsequent write operations exceed allocated memory space. This improper memory management creates opportunities for attackers to craft PDF documents with specific malformed structures that trigger the buffer overflow condition during normal processing operations. The vulnerability is particularly concerning because it can be triggered by simply opening a malicious PDF file, requiring no special user interaction beyond the initial document access.
The operational impact of CVE-2017-17866 extends beyond simple denial of service to potentially enable more sophisticated attacks depending on the execution environment. Remote attackers can leverage this vulnerability to cause application crashes, leading to service disruption and denial of access to legitimate users. In some scenarios, the buffer overflow might be exploitable for arbitrary code execution, especially when the affected system runs with sufficient privileges or when combined with other vulnerabilities. The vulnerability affects any system utilizing Artifex MuPDF library versions before 1.12.0 for PDF processing, including web applications, document viewers, and mobile platforms that depend on this library for PDF rendering and manipulation. This makes the impact widespread across various industries including financial services, healthcare, and government sectors that rely on PDF document handling.
Organizations should immediately upgrade to Artifex MuPDF version 1.12.0 or later to remediate this vulnerability, as this release includes proper buffer boundary checking and length validation during repair operations. System administrators should also implement defensive measures such as PDF content filtering and sandboxing techniques to limit the potential impact of exploitation attempts. The vulnerability aligns with ATT&CK technique T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter) as it can be used to execute malicious code through document processing. Additional mitigations include implementing network-based filtering to block suspicious PDF content and conducting regular security assessments of systems that process PDF documents. Security teams should also monitor for exploitation attempts through network traffic analysis and implement proper incident response procedures to handle potential exploitation events. The vulnerability demonstrates the critical importance of proper memory management in document processing libraries and highlights the need for comprehensive input validation in all PDF parsing operations.