CVE-2018-20425 in libming
Summary
by MITRE
libming 0.4.8 has a NULL pointer dereference in the pushdup function of the decompile.c file.
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Analysis
by VulDB Data Team • 09/09/2025
The vulnerability identified as CVE-2018-20425 represents a critical NULL pointer dereference flaw within the libming library version 0.4.8. This library serves as a SWF (Shockwave Flash) file manipulation tool that allows developers and security researchers to analyze, create, and modify flash content. The specific issue resides in the decompile.c source file within the pushdup function, which handles the processing of SWF bytecode operations. When malformed or malicious SWF files are processed by applications utilizing this library, the function fails to properly validate pointer references before dereferencing them, creating a potential crash condition that could be exploited by attackers.
The technical nature of this vulnerability stems from improper input validation within the SWF decompilation process. The pushdup function, which is responsible for handling stack operations in SWF bytecode, attempts to access memory locations without first verifying that the pointers contain valid addresses. This type of flaw falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. The vulnerability occurs during the parsing of SWF files where the library encounters unexpected bytecode structures that cause the function to proceed with a NULL pointer reference, leading to an immediate program termination or system crash.
From an operational standpoint, this vulnerability presents significant risks to systems that rely on libming for SWF file analysis or processing. Applications using this library could be subjected to denial of service attacks where adversaries craft malicious SWF files designed to trigger the NULL pointer dereference, causing legitimate applications to crash repeatedly. This makes the vulnerability particularly dangerous in environments where continuous availability is critical, such as web applications, content management systems, or security analysis tools that process user-uploaded SWF files. The impact extends beyond simple crashes as this type of vulnerability could potentially be leveraged in more sophisticated attack vectors, especially when combined with other memory corruption issues.
Organizations utilizing libming version 0.4.8 should prioritize immediate mitigation through patching or upgrading to a newer version that addresses this NULL pointer dereference. The recommended approach involves updating to the latest stable release of libming where the pushdup function has been properly validated to handle edge cases and malformed input. Additionally, implementing proper input sanitization measures within applications that use this library can provide an additional layer of defense. Security teams should also consider deploying runtime monitoring solutions that can detect abnormal program termination patterns or memory access violations that might indicate exploitation attempts. This vulnerability aligns with ATT&CK technique T1499 which covers network disruption and system resource exhaustion through denial of service methods, making it a critical concern for maintaining system availability and security posture.