CVE-2018-7870 in libming
Summary
by MITRE
An invalid memory address dereference was discovered in getString in util/decompile.c in libming 0.4.8 for CONSTANT16 data. The vulnerability causes a segmentation fault and application crash, which leads to denial of service.
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Analysis
by VulDB Data Team • 02/17/2023
The vulnerability identified as CVE-2018-7870 represents a critical memory safety issue within the libming library version 0.4.8, specifically affecting the getString function located in util/decompile.c. This flaw manifests as an invalid memory address dereference when processing CONSTANT16 data structures, creating a scenario where the application attempts to access memory locations that are either unmapped or protected, resulting in a segmentation fault. The libming library serves as a SWF (Small Web Format) file manipulation library used for parsing and generating flash content, making this vulnerability particularly concerning for applications that process untrusted SWF files from external sources.
The technical implementation of this vulnerability stems from inadequate input validation within the decompilation process of SWF files. When the getString function encounters malformed CONSTANT16 data structures, it fails to properly validate memory pointers before dereferencing them, leading to a direct memory access violation. This type of flaw falls under the CWE-476 category of NULL Pointer Dereference, though specifically manifests as an invalid memory address dereference rather than a simple null pointer access. The vulnerability operates at the binary parsing layer where the library attempts to extract string data from SWF file structures, and when confronted with unexpected data formats, the memory management logic fails catastrophically.
The operational impact of CVE-2018-7870 extends beyond simple application crashes to encompass broader denial of service scenarios that can affect entire systems relying on libming for SWF processing. Any application that utilizes libming to parse SWF files, including web browsers, content management systems, or media processing applications, becomes vulnerable to remote exploitation if they accept untrusted SWF input. The segmentation fault triggered by this vulnerability can cause cascading failures in applications that do not properly handle such crashes, potentially leading to system instability or complete service outages. This vulnerability is particularly dangerous in server environments where SWF file processing is automated or part of content ingestion pipelines.
Mitigation strategies for this vulnerability require immediate patching of libming to version 0.4.9 or later, which contains the necessary fixes for proper memory validation. Organizations should implement input sanitization measures that validate SWF file structures before processing, including implementing bounds checking and memory access validation routines. Additionally, deploying application-level protections such as sandboxing mechanisms and memory protection features can help contain the impact of such vulnerabilities. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation through memory corruption and denial of service attacks, though it primarily functions as a remote code execution vector that can be exploited without user interaction. System administrators should also consider implementing network-based intrusion detection systems that can identify malformed SWF file patterns and prevent their processing until proper patches are deployed across all affected systems.