CVE-2018-7867 in libming
Summary
by MITRE
There is a heap-based buffer overflow in the getString function of util/decompile.c in libming 0.4.8 during a RegisterNumber sprintf. A Crafted input will lead to a denial of service attack.
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Analysis
by VulDB Data Team • 02/17/2023
The heap-based buffer overflow vulnerability identified as CVE-2018-7867 exists within the libming 0.4.8 library, specifically in the getString function located in util/decompile.c. This vulnerability manifests during the execution of a RegisterNumber sprintf operation where the application fails to properly validate input length before copying data into a heap-allocated buffer. The flaw represents a classic buffer overflow condition that occurs when the destination buffer cannot accommodate the source data, leading to memory corruption beyond the allocated boundaries. The vulnerability is particularly concerning as it affects a core decompression utility function that processes SWF file data, making it exploitable through malformed input files that could be encountered during normal software operation.
The technical implementation of this vulnerability stems from inadequate bounds checking in the string formatting operation that occurs when processing register numbers within SWF file decompilation. When a crafted input is provided, the sprintf function attempts to write more data than the allocated buffer can contain, causing adjacent memory to be overwritten. This heap-based overflow creates unpredictable behavior that can result in application crashes, memory corruption, or potentially more severe consequences depending on the execution environment. The vulnerability classifies under CWE-121 as a stack-based buffer overflow, though the heap-based nature indicates the overflow occurs in heap memory rather than stack memory. The specific function path involves the getString utility being called during SWF file processing, where register number information is extracted and formatted into strings.
The operational impact of this vulnerability extends beyond simple denial of service as it represents a potential vector for more sophisticated attacks. While the immediate effect is a denial of service through application crash, the heap corruption could potentially be leveraged to execute arbitrary code if proper memory protection mechanisms are not in place. The vulnerability affects any system utilizing libming 0.4.8 for SWF file processing, including web applications, desktop software, and content management systems that handle Flash content. Attackers could craft malicious SWF files designed to trigger this condition, potentially causing service disruption across multiple applications that depend on the vulnerable library. The exploitability of this vulnerability is relatively straightforward since it requires only the provision of malformed input to the affected function, making it a significant concern for applications processing untrusted SWF content.
Mitigation strategies for CVE-2018-7867 should prioritize immediate patching of the libming library to version 0.4.9 or later, which contains the necessary fixes for the buffer overflow condition. Organizations should also implement input validation measures that restrict the length of register numbers and other numeric data processed by the affected library. The implementation of stack canaries, address space layout randomization, and other memory protection mechanisms can provide additional defense in depth. Security monitoring should include detection of unusual memory access patterns and application crashes that may indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to T1203 as a process injection technique that could be used in conjunction with other attack vectors, though the primary threat is the direct denial of service impact. System administrators should also consider implementing network segmentation and application whitelisting to limit the potential impact of successful exploitation attempts.