CVE-2018-20428 in libming
Summary
by MITRE
libming 0.4.8 has a NULL pointer dereference in the strlenext function of the decompile.c file, a different vulnerability than CVE-2018-7874.
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Analysis
by VulDB Data Team • 09/08/2025
The vulnerability identified as CVE-2018-20428 affects libming version 0.4.8, a library used for processing flash media files and creating swf files. This issue manifests as a NULL pointer dereference within the strlenext function located in the decompile.c source file, representing a distinct security flaw from CVE-2018-7874 which affected the same library. The vulnerability arises during the decompilation process when the library attempts to process malformed or specially crafted input files that trigger unexpected behavior in the string length calculation routine.
The technical flaw occurs when the strlenext function receives a NULL pointer as input and attempts to dereference it without proper validation checks. This type of vulnerability falls under the Common Weakness Enumeration category CWE-476, which specifically addresses NULL pointer dereference conditions that can lead to application crashes or potentially more severe consequences. The function's lack of input validation creates an execution path where the program attempts to access memory at address zero, causing an immediate crash that terminates the application process and potentially exposing the system to denial of service attacks.
The operational impact of this vulnerability extends beyond simple application instability, as it can be exploited by attackers to perform denial of service attacks against systems that rely on libming for processing flash content. When an attacker crafts a malicious file that triggers the NULL pointer dereference, the target system's application using libming will crash, potentially affecting services that depend on this library for processing user-uploaded content or automated media handling. This vulnerability is particularly concerning in web applications or content processing services where untrusted input is common, as it can be leveraged to disrupt service availability.
Mitigation strategies for CVE-2018-20428 should focus on immediate code-level fixes including input validation and proper NULL pointer checking within the strlenext function. Developers should implement defensive programming practices that verify all input parameters before dereferencing pointers, which aligns with ATT&CK technique T1203 for exploitation of input validation weaknesses. Additionally, system administrators should ensure that all instances of libming are updated to versions that contain the patched strlenext function, while also implementing proper input sanitization and sandboxing measures for any applications that process untrusted flash content. The fix should also include comprehensive testing of edge cases and malformed inputs to prevent similar issues from occurring in other parts of the library's codebase.