CVE-2016-8728 in MuPDF
Summary
by MITRE
An exploitable heap out of bounds write vulnerability exists in the Fitz graphical library part of the MuPDF renderer. A specially crafted PDF file can cause a out of bounds write resulting in heap metadata and sensitive process memory corruption leading to potential code execution. Victim needs to open the specially crafted file in a vulnerable reader in order to trigger this vulnerability.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 03/07/2023
The vulnerability identified as CVE-2016-8728 represents a critical heap out of bounds write flaw within the Fitz graphical library component of the MuPDF document rendering system. This vulnerability resides in the PDF parsing and rendering functionality that processes graphical elements and layout information contained within PDF documents. The Fitz library serves as the core rendering engine responsible for displaying PDF content including text, images, and vector graphics, making it a prime target for exploitation due to its widespread use in PDF viewers and document processing applications. The flaw manifests when the renderer encounters malformed or specially crafted PDF files that contain maliciously constructed graphical data structures.
The technical implementation of this vulnerability stems from insufficient bounds checking within the memory allocation and manipulation routines of the Fitz library. When processing certain PDF graphical objects, the library fails to validate the size and boundaries of heap-allocated memory regions before performing write operations. This allows an attacker to construct a PDF file containing oversized or malformed graphical elements that exceed the allocated memory boundaries, resulting in a heap overflow condition. The out of bounds write specifically targets heap metadata structures and adjacent memory regions containing sensitive process information, effectively corrupting the memory layout and potentially allowing arbitrary code execution. The vulnerability is classified under CWE-787 as an out-of-bounds write, which represents one of the most dangerous classes of memory corruption vulnerabilities in software systems.
The operational impact of this vulnerability extends far beyond simple document rendering failures, as it enables remote code execution when victims open malicious PDF files in vulnerable applications. Attackers can leverage this vulnerability to execute arbitrary code within the context of the PDF viewer process, potentially leading to complete system compromise. The attack requires only that a user open the specially crafted PDF file, making it particularly dangerous in phishing campaigns or malicious document distribution scenarios. The vulnerability affects numerous PDF readers and document processing applications that utilize the MuPDF library, including popular tools such as Sumatra PDF, MuPDF itself, and various mobile applications that incorporate this rendering engine. The exploitation process typically involves crafting a PDF file with carefully constructed graphical elements that trigger the memory corruption during normal document rendering operations, with the potential for privilege escalation depending on the target system configuration.
Mitigation strategies for CVE-2016-8728 primarily focus on immediate software updates and patches provided by vendors, as the vulnerability requires no user interaction beyond opening the malicious document. Organizations should prioritize patch management to ensure all affected PDF readers and document processing applications are updated with the latest security fixes from their respective vendors. Additionally, implementing defensive measures such as sandboxing PDF viewers, restricting file type execution permissions, and deploying network-based intrusion detection systems can help reduce the attack surface. Security professionals should also consider employing automated PDF analysis tools that can detect and quarantine potentially malicious documents before they reach end users. The vulnerability aligns with ATT&CK technique T1203 as a means of gaining initial access through malicious document files, and represents a classic example of how graphical rendering libraries can become attack vectors in modern software ecosystems. Regular security assessments of document processing applications and maintaining up-to-date threat intelligence regarding similar vulnerabilities in graphical rendering components should be part of comprehensive cybersecurity programs to prevent exploitation of similar heap-based memory corruption flaws.