CVE-2018-11095 in libming
Summary
by MITRE
The decompileJUMP function in decompile.c in libming through 0.4.8 mishandles cases where the header indicates a file size greater than the actual size, which allows remote attackers to cause a denial of service (Segmentation fault and application crash) or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 03/13/2023
The vulnerability identified as CVE-2018-11095 resides within the libming library version 0.4.8 and earlier, specifically within the decompileJUMP function located in decompile.c. This flaw represents a classic buffer over-read condition that occurs when processing SWF (Small Web Format) files, which are commonly used for multimedia content on web platforms. The issue manifests when the library encounters a malformed SWF file where the file header contains a declared size that exceeds the actual file content, creating a scenario where the decompilation process attempts to access memory beyond the allocated boundaries.
The technical implementation of this vulnerability stems from inadequate input validation within the decompileJUMP function, which fails to properly verify the relationship between the header-specified file size and the actual file content during the parsing process. When the library attempts to process such malformed files, it follows the header-specified size parameter to allocate or access memory regions, leading to segmentation faults when the actual file data ends before the expected boundary. This condition falls under the Common Weakness Enumeration category CWE-129, which deals with insufficient validation of length of input buffers, and specifically relates to improper handling of buffer boundaries during file parsing operations.
From an operational perspective, this vulnerability presents significant risks to applications that utilize libming for SWF file processing, particularly those exposed to untrusted input from web users or external sources. Remote attackers can exploit this weakness by crafting malicious SWF files with manipulated header information, potentially causing denial of service conditions that result in application crashes and system instability. The impact extends beyond simple service disruption as the vulnerability could theoretically be leveraged to execute arbitrary code if the memory corruption leads to exploitable conditions, though the primary risk identified is the segmentation fault and application crash behavior. This vulnerability directly maps to ATT&CK technique T1203, which involves legitimate programs being used for code execution through manipulation of file parsing routines.
The mitigation strategy for this vulnerability involves upgrading to libming version 0.4.9 or later, where the developers have implemented proper bounds checking and input validation within the decompileJUMP function. Organizations should also implement defensive programming practices such as validating file headers against actual content size before processing, implementing proper error handling for malformed input, and employing sandboxing techniques when processing untrusted SWF files. Additionally, network segmentation and access controls should be enforced to limit exposure to potentially malicious file uploads, while regular security audits of file processing components should be conducted to identify similar buffer handling issues within the application stack. The fix demonstrates proper input validation principles that align with secure coding guidelines and address the fundamental weakness in boundary checking that allowed the memory access violation to occur.