CVE-2018-5251 in libming
Summary
by MITRE
In libming 0.4.8, there is an integer signedness error vulnerability (left shift of a negative value) in the readSBits function (util/read.c). Remote attackers can leverage this vulnerability to cause a denial of service via a crafted swf file.
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Analysis
by VulDB Data Team • 01/20/2023
The vulnerability identified as CVE-2018-5251 resides within the libming library version 0.4.8, a software library designed for creating and manipulating Shockwave Flash files. This flaw manifests as an integer signedness error specifically within the readSBits function located in util/read.c. The core issue occurs when the function processes left shift operations on negative values, creating a scenario where signed integer arithmetic behaves unexpectedly and potentially leads to undefined behavior. Such vulnerabilities are particularly dangerous in multimedia processing libraries that handle untrusted input files from external sources.
The technical implementation of this vulnerability exploits the fundamental flaw in how signed integers are handled during bit manipulation operations. When a negative value undergoes a left shift operation, the behavior becomes implementation-defined according to the c standard, potentially causing the program to crash or behave unpredictably. In the context of flash file processing, this occurs when parsing malformed swf files that contain crafted bitstream data designed to trigger the specific code path leading to the signed integer overflow condition. The vulnerability specifically targets the signedness assumption in the bit reading logic where negative values are not properly validated before arithmetic operations.
From an operational perspective, this vulnerability presents a significant denial of service risk for applications relying on libming for flash file processing. Remote attackers can craft malicious swf files that, when processed by vulnerable applications, will cause the application to crash or become unresponsive. The impact extends beyond simple service interruption as it can affect any software ecosystem that utilizes libming for flash content handling, including web applications, content management systems, and multimedia processing tools. The vulnerability's remote exploitability means that attackers do not need local access to cause disruption, making it particularly concerning for web-facing applications.
The vulnerability aligns with CWE-128, which addresses "Unsigned to Signed Conversion Error" and falls under the broader category of integer overflow vulnerabilities. From an attack framework perspective, this vulnerability could be categorized under ATT&CK technique T1203, "Exploitation for Client Execution," as it enables remote code execution through crafted file manipulation. The remediation strategy requires immediate patching of libming to version 0.4.9 or later where the integer signedness error has been corrected. Additionally, input validation and sanitization measures should be implemented at the application level to prevent processing of untrusted swf files, along with proper error handling to prevent crash propagation. Organizations should also consider implementing network segmentation and access controls to limit exposure to potentially malicious swf file inputs.