CVE-2018-19881 in MuPDF
Summary
by MITRE
In Artifex MuPDF 1.14.0, svg/svg-run.c allows remote attackers to cause a denial of service (recursive calls followed by a fitz/xml.c fz_xml_att crash from excessive stack consumption) via a crafted svg file, as demonstrated by mupdf-gl.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/12/2024
The vulnerability identified as CVE-2018-19881 affects Artifex MuPDF version 1.14.0 and represents a denial of service flaw that stems from improper handling of SVG (Scalable Vector Graphics) files during parsing operations. This issue specifically resides within the svg/svg-run.c component of the MuPDF library, which is widely used for rendering PDF documents and various vector graphics formats. The vulnerability manifests when processing specially crafted SVG files that contain recursive structures or excessive nesting, leading to a cascade of function calls that ultimately results in stack exhaustion and subsequent application crash.
The technical root cause of this vulnerability lies in the lack of proper recursion depth limiting and stack consumption monitoring within the SVG parsing logic. When MuPDF encounters an SVG file with deeply nested elements or circular references, the parsing functions in svg-run.c continue to make recursive calls without adequate bounds checking. This recursive behavior eventually leads to the exhaustion of available stack memory, causing the application to crash at the fz_xml_att function in fitz/xml.c. The crash occurs because the XML parser within the fitz module attempts to process attributes from the malformed SVG structure, but the excessive stack consumption prevents proper execution flow. This vulnerability falls under CWE-674, which specifically addresses "Uncontrolled Recursion" and represents a classic stack overflow scenario where recursive function calls are not properly bounded.
The operational impact of CVE-2018-19881 extends beyond simple application instability, as it can be exploited by remote attackers to perform denial of service attacks against systems processing SVG content. This vulnerability affects any application that utilizes MuPDF for rendering or processing SVG files, including web browsers, document viewers, and content management systems that support SVG format. The attack vector is particularly concerning because it requires no special privileges or authentication, making it accessible to anyone capable of delivering a malicious SVG file to a vulnerable system. When exploited, the vulnerability can cause complete application termination, requiring manual intervention to restore service. In environments where MuPDF is used for document processing, this could lead to significant operational disruptions, particularly in high-volume document handling systems or automated processing pipelines.
Mitigation strategies for CVE-2018-19881 should focus on both immediate defensive measures and long-term architectural improvements. The most effective immediate solution involves upgrading to a patched version of MuPDF that addresses the recursion depth limitations and implements proper stack consumption monitoring. Organizations should also implement content filtering mechanisms that scan SVG files for suspicious nesting patterns or excessive recursion before processing them through MuPDF. Additionally, deploying runtime protections such as stack canaries or stack overflow detection mechanisms can help prevent exploitation of similar vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique related to "Resource Hijacking: Unnecessary Resource Consumption" and represents a classic example of how parsing vulnerabilities can be leveraged for denial of service attacks. The vulnerability also aligns with T1059.007 for "Command and Scripting Interpreter: JavaScript" as SVG files can contain embedded scripting elements that contribute to the recursive behavior, though in this case the primary issue stems from structural recursion rather than script execution. System administrators should also consider implementing network segmentation and access controls to limit exposure of vulnerable systems to untrusted SVG content, while regular security audits should be conducted to identify other potential parsing vulnerabilities in similar libraries.