CVE-2016-8729 in MuPDF
Summary
by MITRE
An exploitable memory corruption vulnerability exists in the JBIG2 parser of Artifex MuPDF 1.9. A specially crafted PDF can cause a negative number to be passed to a memset resulting in memory corruption and potential code execution. An attacker can specially craft a PDF and send to the victim to trigger this vulnerability.
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Analysis
by VulDB Data Team • 03/07/2023
The vulnerability identified as CVE-2016-8729 represents a critical memory corruption flaw within the JBIG2 parser component of Artifex MuPDF version 1.9. This issue arises from improper input validation and handling of malformed JBIG2 data structures within PDF documents, creating a pathway for remote code execution through crafted malicious files. The vulnerability specifically manifests when a negative value is passed to the memset function, which is a fundamental memory operation used to fill blocks of memory with a specific value. This particular flaw demonstrates the dangerous intersection of buffer management errors and integer overflow conditions that can be exploited by adversaries to manipulate memory layout and execute arbitrary code.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read scenarios. When a malicious PDF document is processed by MuPDF, the JBIG2 parser fails to properly validate the size parameters of JBIG2 data segments, allowing an attacker to inject negative values into memory operations. The memset function, which expects a positive integer for its size parameter, receives a negative value that causes the function to behave unpredictably, potentially leading to memory corruption that can be leveraged for privilege escalation or arbitrary code execution. This type of vulnerability is particularly dangerous because it can be triggered through normal document processing operations without requiring special privileges or user interaction beyond opening the malicious file.
From an operational impact perspective, this vulnerability affects any system running MuPDF version 1.9 or earlier that processes PDF documents, including web applications, document viewers, and mobile platforms that utilize this library. The attack vector is particularly concerning as it requires no user interaction beyond opening the malicious document, making it suitable for drive-by download scenarios and automated exploitation campaigns. The vulnerability's classification under the MITRE ATT&CK framework would align with techniques such as T1059 for command and scripting interpreter and T1068 for exploit for privilege escalation, as successful exploitation could allow attackers to gain control over the affected system. The memory corruption effects can manifest in various ways including application crashes, memory corruption that may lead to denial of service, or more severe scenarios where attackers can execute code with the privileges of the affected application.
Mitigation strategies for CVE-2016-8729 should prioritize immediate patching of all affected MuPDF installations to version 1.10 or later where this vulnerability has been resolved. Organizations should implement defensive measures including PDF content filtering, sandboxing of document processing environments, and network-based intrusion detection systems that can identify and block suspicious PDF file patterns. Additionally, security teams should conduct comprehensive vulnerability assessments to identify all systems that may be running affected versions of MuPDF, particularly those that process untrusted PDF content. The remediation approach should follow industry best practices for patch management and application hardening, ensuring that all affected systems are updated and that proper monitoring is in place to detect potential exploitation attempts. Organizations should also consider implementing application whitelisting policies and restricting PDF processing to trusted environments to reduce the attack surface and prevent unauthorized exploitation of this memory corruption vulnerability.