CVE-2017-16883 in libming
Summary
by MITRE
The outputSWF_TEXT_RECORD function in util/outputscript.c in libming <= 0.4.8 is vulnerable to a NULL pointer dereference, which may allow attackers to cause a denial of service via a crafted swf file.
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Analysis
by VulDB Data Team • 01/11/2023
The vulnerability identified as CVE-2017-16883 resides within the libming library version 0.4.8 and earlier, specifically within the outputSWF_TEXT_RECORD function located in util/outputscript.c. This library serves as a SWF (Small Web Format) file manipulation toolset that allows developers to create and modify flash content programmatically. The flaw manifests as a NULL pointer dereference condition that occurs when processing specially crafted SWF files containing malformed text records. When the function attempts to dereference a pointer that has not been properly initialized or has been set to NULL, the application crashes due to the absence of proper null checks in the code structure.
The technical implementation of this vulnerability stems from inadequate input validation and error handling within the SWF parsing routine. The outputSWF_TEXT_RECORD function processes text elements within SWF files without sufficient verification of the text record structure's integrity. When encountering a malformed text record that fails to properly initialize certain data structures or pointers, the function proceeds to access these uninitialized memory locations, resulting in a segmentation fault or access violation. This behavior aligns with CWE-476 which specifically addresses NULL pointer dereference vulnerabilities, where a null pointer is dereferenced without proper validation. The vulnerability represents a classic denial of service scenario where an attacker can craft a malicious SWF file that triggers the NULL pointer dereference when processed by applications utilizing libming.
The operational impact of this vulnerability extends beyond simple service disruption as it can be exploited in various contexts where SWF files are processed or rendered. Applications that utilize libming for SWF file generation, conversion, or analysis become susceptible to this attack vector, potentially leading to complete application crashes or system instability. The vulnerability is particularly concerning in web applications or content management systems that accept user-uploaded SWF files, as attackers could leverage this flaw to disrupt services or perform denial of service attacks against legitimate users. The exploitability of this vulnerability is relatively straightforward since it requires only the creation of a malformed SWF file, making it accessible to attackers with basic knowledge of SWF file structure and the specific memory access pattern that triggers the flaw.
Mitigation strategies for CVE-2017-16883 primarily focus on immediate software updates and code-level defensive programming practices. The most effective approach involves upgrading to libming version 0.4.9 or later, where the NULL pointer dereference has been addressed through proper input validation and null pointer checks. System administrators should implement immediate patch management procedures to ensure all affected systems receive the necessary updates. Additionally, defensive programming measures should be implemented at the application level, including input sanitization, proper error handling, and validation of all parsed SWF file structures before processing. Organizations utilizing libming in their applications should also consider implementing sandboxing techniques or file validation layers that can detect and reject potentially malicious SWF content before it reaches the vulnerable library functions. This vulnerability demonstrates the importance of proper memory management and input validation practices, aligning with ATT&CK technique T1499 which covers network denial of service attacks and T1059 which addresses execution through command and scripting interpreters, particularly in environments where SWF processing is involved.