CVE-2017-9988 in libming
Summary
by MITRE
The readEncUInt30 function in util/read.c in libming 0.4.8 mishandles memory allocation. A crafted input will lead to a remote denial of service (NULL pointer dereference) attack against parser.c.
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Analysis
by VulDB Data Team • 12/09/2022
The vulnerability identified as CVE-2017-9988 resides within the libming library version 0.4.8, specifically in the readEncUInt30 function located in util/read.c. This library serves as a SWF (Small Web Format) file manipulation library commonly used for parsing and generating flash content. The flaw manifests in how the function handles memory allocation when processing encoded unsigned 30-bit integers, creating a critical weakness that can be exploited remotely. The issue occurs during the parsing phase where maliciously crafted input data causes the function to fail in proper memory management, ultimately leading to a NULL pointer dereference condition.
The technical implementation of this vulnerability stems from improper memory allocation handling within the readEncUInt30 function. When the parser encounters malformed input data, the function fails to correctly allocate memory for the parsed value, resulting in a situation where a NULL pointer is dereferenced during subsequent operations in parser.c. This type of error falls under CWE-476 which specifically addresses NULL Pointer Dereference, representing a fundamental memory safety issue that can be exploited to crash applications. The vulnerability demonstrates a classic case of inadequate input validation and memory management, where the library fails to properly handle edge cases in its parsing logic.
The operational impact of this vulnerability extends beyond simple application crashes, presenting a significant remote denial of service threat to systems utilizing libming for SWF file processing. Attackers can craft specific SWF files containing malformed encoded integers that trigger the NULL pointer dereference when the library attempts to parse these inputs. This creates a scenario where legitimate users or automated systems processing SWF content could experience service disruption, potentially affecting web applications, content management systems, or any software that relies on libming for flash content handling. The vulnerability's remote exploitability means that malicious actors can trigger the condition without requiring local access, making it particularly dangerous in web-facing applications.
Mitigation strategies for CVE-2017-9988 should prioritize immediate patching of affected libming installations to version 0.4.9 or later, which contains the necessary fixes for the memory allocation handling. System administrators should implement input validation measures to sanitize SWF file content before processing, particularly when dealing with untrusted inputs from external sources. The vulnerability's classification aligns with ATT&CK technique T1499.004 which covers Network Denial of Service, and organizations should consider implementing network segmentation and monitoring to detect potential exploitation attempts. Additionally, application developers should adopt defensive programming practices such as input sanitization, proper error handling, and memory allocation validation to prevent similar issues in their own codebases. The remediation process should also include thorough testing of patched libraries to ensure that the fix does not introduce regressions in functionality while maintaining the library's core SWF processing capabilities.