CVE-2017-16711 in SWFTools
Summary
by MITRE
The swf_DefineLosslessBitsTagToImage function in lib/modules/swfbits.c in SWFTools 0.9.2 mishandles an uncompress failure, which allows remote attackers to cause a denial of service (NULL pointer dereference and application crash) because of extractDefinitions in lib/readers/swf.c and fill_line_bitmap in lib/devices/render.c, as demonstrated by swfrender.
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Analysis
by VulDB Data Team • 01/10/2023
The vulnerability identified as CVE-2017-16711 resides within SWFTools version 0.9.2, specifically within the swf_DefineLosslessBitsTagToImage function located in lib/modules/swfbits.c. This flaw represents a critical denial of service vulnerability that can be exploited remotely by attackers to crash applications that utilize SWFTools for processing flash content. The issue stems from improper handling of decompression failures during the processing of SWF files, creating a scenario where a malformed input can trigger application instability.
The technical root cause involves the mishandling of an uncompress failure condition within the SWF processing pipeline. When the extractDefinitions function in lib/readers/swf.c encounters a decompression error during SWF file parsing, and subsequently when fill_line_bitmap in lib/devices/render.c attempts to process the corrupted data, the application fails to properly validate error conditions before proceeding with operations. This failure results in a NULL pointer dereference, which immediately terminates the application process and leads to a complete denial of service condition. The vulnerability is particularly concerning because it can be triggered through simple manipulation of SWF file content without requiring complex exploitation techniques.
The operational impact of this vulnerability extends beyond simple service disruption to potentially affect any system or application that relies on SWFTools for processing flash content. Organizations using swfrender or similar tools for rendering SWF files, converting flash content, or processing multimedia assets become vulnerable to this attack vector. The remote nature of the exploit means that attackers can trigger the vulnerability from external systems without requiring local access, making it particularly dangerous in networked environments. The crash occurs during the rendering phase of SWF processing, which can affect web servers, content management systems, or any automated processes that handle SWF file uploads or conversions.
Mitigation strategies for this vulnerability include immediate patching of SWFTools to version 0.9.3 or later, which contains the necessary fixes for proper error handling during decompression failures. System administrators should also implement input validation measures to prevent malformed SWF files from reaching the processing pipeline, including content filtering and sandboxing techniques. Additionally, organizations should consider implementing network segmentation and access controls to limit exposure of systems that process SWF content. The vulnerability aligns with CWE-476, which describes NULL pointer dereference conditions, and can be categorized under ATT&CK technique T1499.004 for network denial of service attacks. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other multimedia processing libraries and tools that may exhibit comparable error handling flaws during decompression operations.