CVE-2018-8963 in libming
Summary
by MITRE
In libming 0.4.8, the decompileGETVARIABLE function of decompile.c has a use-after-free. Remote attackers could leverage this vulnerability to cause a denial of service via a crafted swf file.
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Analysis
by VulDB Data Team • 02/24/2023
The vulnerability identified as CVE-2018-8963 resides within the libming library version 0.4.8, specifically within the decompileGETVARIABLE function located in the decompile.c source file. This issue represents a classic use-after-free vulnerability that occurs when memory previously allocated and freed is subsequently accessed or referenced by the application. The libming library serves as a SWF (Small Web Format) file manipulation library used for parsing and generating Shockwave Flash content, making it a critical component in multimedia processing applications. The flaw manifests during the decompilation process of SWF files, where the function fails to properly manage memory references after deallocation, creating a scenario where freed memory locations may still be accessed by subsequent operations.
The technical exploitation of this vulnerability occurs when remote attackers craft malicious SWF files designed to trigger the specific code path involving the decompileGETVARIABLE function. When the vulnerable library processes these crafted files, the use-after-free condition leads to undefined behavior that typically results in application crashes or denial of service conditions. The vulnerability stems from improper memory management practices where the function does not adequately track or invalidate references to previously freed memory blocks. This type of memory corruption vulnerability falls under CWE-416, which specifically addresses the use of freed memory condition, and represents a fundamental flaw in the library's memory lifecycle management. The attack vector is particularly concerning as it operates over a network channel, allowing remote adversaries to exploit the vulnerability without requiring local access or user interaction.
The operational impact of CVE-2018-8963 extends beyond simple denial of service scenarios, as it can severely disrupt services that depend on the libming library for SWF processing functionality. Applications utilizing this library for content analysis, conversion, or preview services may experience complete service interruption when processing malicious SWF files. The vulnerability affects systems across multiple platforms where libming is deployed, including web servers, content management systems, and multimedia processing applications. From an attacker perspective, this vulnerability aligns with ATT&CK technique T1203, which involves the use of malicious files to gain access to systems or cause service disruption. The vulnerability's remote exploitability makes it particularly dangerous for web-facing applications that process user-uploaded SWF content, as it can be leveraged to systematically disrupt services or potentially escalate to more severe compromise scenarios.
Mitigation strategies for this vulnerability require immediate patching of the libming library to version 0.4.9 or later, which contains the necessary memory management fixes. Organizations should implement comprehensive input validation for SWF file processing, including strict file format checking and size limitations to reduce the attack surface. Network-based mitigations such as content filtering and sandboxing mechanisms can provide additional protection layers while patches are deployed. The vulnerability highlights the importance of regular security assessments and dependency updates, as use-after-free conditions often indicate broader memory management issues within software libraries. Security teams should also consider implementing monitoring solutions to detect unusual application behavior or crash patterns that may indicate exploitation attempts. System administrators should prioritize patch management processes and ensure that all instances of libming are updated to prevent exploitation, as the vulnerability's remote nature makes it particularly attractive to automated attack systems.