CVE-2021-44591 in libming
Summary
by MITRE • 01/06/2022
In libming 0.4.8, the parseSWF_DEFINELOSSLESS2 function in util/parser.c lacks a boundary check that would lead to denial-of-service attacks via a crafted SWF file.
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Analysis
by VulDB Data Team • 01/09/2022
The vulnerability identified as CVE-2021-44591 affects libming version 0.4.8, a library used for parsing and generating Macromedia Flash files. This issue resides within the parseSWF_DEFINELOSSLESS2 function located in util/parser.c, where a critical boundary check is missing that could be exploited by malicious actors to disrupt system operations. The flaw specifically manifests when processing specially crafted SWF files that contain malformed data structures, creating a potential denial-of-service condition that impacts the stability and availability of applications relying on this library.
The technical implementation of this vulnerability stems from inadequate input validation within the parsing logic of the SWF file format handler. When the parseSWF_DEFINELOSSLESS2 function processes a crafted SWF file, it fails to properly verify array bounds or data structure limits before attempting to access memory locations. This absence of boundary checking creates a scenario where an attacker can construct a SWF file with maliciously formatted data that causes the parser to attempt memory access beyond allocated buffers or valid data regions. Such behavior can result in segmentation faults, memory corruption, or other runtime errors that terminate the application process or render it unresponsive.
From an operational perspective, this vulnerability presents significant risks to systems that utilize libming for SWF file processing, including web applications, content management systems, and multimedia processing platforms. The denial-of-service impact means that legitimate users may experience service interruptions when encountering maliciously crafted Flash content, potentially affecting availability for extended periods. The vulnerability is particularly concerning because SWF files are commonly distributed through web browsers and content delivery networks, making exploitation relatively straightforward. Organizations using this library in production environments face potential business disruption and increased operational overhead as they must address the vulnerability through patching or alternative processing mechanisms.
The vulnerability aligns with CWE-129, which addresses insufficient boundary checking, and represents a classic example of improper input validation in file parsing operations. From an ATT&CK framework perspective, this weakness maps to T1499.004, which covers network disruption through resource exhaustion or system instability. The attack surface is broad given that SWF files were widely used across web applications, making this vulnerability potentially exploitable in numerous contexts where Flash content processing occurs. Mitigation strategies should include immediate patching of the libming library to version 0.4.9 or later, which contains the necessary boundary checks. Additionally, organizations should implement input sanitization measures, deploy network monitoring to detect anomalous SWF file processing patterns, and consider disabling SWF file handling capabilities where possible. The fix should also include comprehensive testing of the patched library to ensure that legitimate SWF files continue to process correctly while preventing the exploitation of this boundary condition vulnerability.