CVE-2018-11017 in libming
Summary
by MITRE
The newVar_N 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 • 02/04/2020
The vulnerability identified as CVE-2018-11017 resides within the libming library version 0.4.8 and earlier, specifically in the newVar_N function located in decompile.c. This flaw represents a classic buffer overflow condition that occurs during the processing of SWF (Small Web Format) files, which are commonly used for multimedia content on web applications. The issue manifests when the library encounters a malformed SWF file where the file header claims a size that exceeds the actual data contained within the file structure. This discrepancy creates a scenario where the application attempts to allocate memory or process data based on incorrect size parameters, leading to unpredictable behavior and system instability.
The technical exploitation of this vulnerability stems from improper input validation and boundary checking within the decompilation process of SWF files. When libming processes a file with a corrupted header indicating an oversized file, the newVar_N function fails to properly verify the integrity of the file structure before attempting to parse or allocate resources. This mismanagement creates a condition where the application may attempt to access memory locations beyond the allocated buffer boundaries, resulting in segmentation faults and subsequent application crashes. The vulnerability operates under CWE-129, which categorizes improper validation of array indices, and aligns with ATT&CK technique T1499.004 for network denial of service attacks. The flaw essentially allows attackers to craft malicious SWF files that trigger memory corruption during the decompilation phase, making it particularly dangerous in environments where automatic SWF processing or previewing occurs.
The operational impact of CVE-2018-11017 extends beyond simple application crashes to potentially enable more sophisticated attack vectors. While the primary effect manifests as denial of service through segmentation faults, the vulnerability's potential for unspecified other impacts suggests that under certain conditions, attackers might be able to execute arbitrary code or manipulate application behavior. This risk is particularly elevated in web applications or content management systems that automatically process or render SWF files without proper sanitization. The vulnerability affects any system utilizing libming for SWF file handling, including web browsers, media players, and content processing applications. Attackers can exploit this weakness by uploading or delivering specially crafted SWF files that contain oversized header information, causing the target application to crash or potentially behave unpredictably.
Mitigation strategies for CVE-2018-11017 require both immediate and long-term approaches to address the underlying memory handling issues within libming. The most effective solution involves upgrading to libming version 0.4.9 or later, where the developers have implemented proper input validation and boundary checking mechanisms to prevent the exploitation of malformed file headers. Organizations should also implement strict file validation protocols that verify file integrity before processing, particularly for user-uploaded content or external media sources. Network-level mitigations include implementing file type restrictions and content filtering to prevent potentially malicious SWF files from reaching vulnerable applications. Additionally, system administrators should consider deploying intrusion detection systems that monitor for unusual memory access patterns or segmentation fault occurrences that might indicate exploitation attempts. The vulnerability highlights the importance of proper memory management and input validation in multimedia processing libraries, as outlined in industry standards for secure coding practices.