CVE-2018-20591 in libming
Summary
by MITRE
A heap-based buffer over-read was discovered in decompileJUMP function in util/decompile.c of libming v0.4.8. A crafted input can cause segmentation faults, leading to denial-of-service, as demonstrated by swftocxx.
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Analysis
by VulDB Data Team • 06/22/2023
The heap-based buffer over-read vulnerability in the decompileJUMP function of libming v0.4.8 represents a critical security flaw that can lead to system instability and denial-of-service conditions. This vulnerability resides within the util/decompile.c file of the libming library, which is commonly used for processing and converting flash swf files. The issue manifests when the decompileJUMP function processes malformed input data, specifically crafted to trigger an out-of-bounds memory read operation. The vulnerability is particularly concerning as it can be exploited through the swftocxx utility, which serves as a bridge between flash files and c++ code generation, making it accessible to attackers who can manipulate input parameters.
The technical implementation of this flaw involves improper bounds checking within the decompileJUMP function where the code attempts to read memory locations beyond the allocated buffer boundaries. This over-read condition occurs when processing certain jump instructions within flash file structures, causing the application to access memory that has not been properly allocated or validated. The vulnerability can be categorized under CWE-125 as an out-of-bounds read, which is a well-documented class of memory safety issues that can lead to unpredictable behavior and system crashes. The heap-based nature of the vulnerability indicates that the memory corruption occurs in the heap allocation region, making it particularly dangerous as it can potentially corrupt heap metadata and lead to more severe exploitation scenarios.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions, as it can cause segmentation faults that result in application crashes and system instability. When exploited through the swftocxx utility, attackers can craft malicious flash files that trigger the buffer over-read condition, leading to complete application termination and preventing legitimate users from accessing the service. This vulnerability particularly affects systems that process untrusted flash content, making it a significant concern for web applications, content management systems, and any software that relies on libming for flash file processing. The exploitability of this vulnerability is enhanced by the fact that it requires minimal input manipulation to trigger, making it an attractive target for automated exploitation tools.
Mitigation strategies for this vulnerability should focus on immediate patching of the affected libming library to version 0.4.9 or later, which contains the necessary bounds checking fixes. Organizations should implement input validation measures that sanitize all flash file inputs before processing, particularly focusing on jump instruction validation and buffer size verification. The implementation of address sanitizers and memory debugging tools can help detect similar issues in other parts of the codebase, while runtime protections such as stack canaries and heap metadata validation can provide additional defense-in-depth measures. System administrators should also consider implementing network segmentation and access controls to limit exposure to potentially malicious flash content, and regular security assessments should be conducted to identify other potential buffer over-read vulnerabilities within the software ecosystem. This vulnerability demonstrates the importance of thorough input validation and bounds checking in memory management operations, aligning with ATT&CK technique T1059.007 for defense evasion through memory corruption and T1499.004 for denial-of-service attacks through application crashes.