CVE-2018-5684 in libav
Summary
by MITRE
In Libav 12.1, there is an invalid memcpy call in the ff_mov_read_stsd_entries function of libavformat/mov.c. Remote attackers could leverage this vulnerability to cause a denial of service (segmentation fault) and program failure with a crafted avi file.
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Analysis
by VulDB Data Team • 12/23/2019
The vulnerability identified as CVE-2018-5684 represents a critical memory corruption flaw within the Libav multimedia framework version 12.1. This issue manifests in the ff_mov_read_stsd_entries function located within the libavformat/mov.c source file, where an invalid memcpy operation is executed during the processing of multimedia file headers. The flaw specifically impacts the handling of avi file formats and demonstrates how improper memory management can lead to system instability and potential exploitation by malicious actors. The vulnerability falls under the category of memory safety issues and represents a classic example of buffer over-read conditions that can occur when developers fail to properly validate input data before performing memory operations.
The technical implementation of this vulnerability stems from inadequate bounds checking within the MOV file format parser. When processing crafted avi files, the ff_mov_read_stsd_entries function attempts to copy memory blocks without sufficient validation of the source buffer boundaries or destination memory allocation sizes. This invalid memcpy call occurs during the parsing of sample description entries within the MOV container format, which is commonly used in avi files and other multimedia formats. The flaw creates a scenario where the application attempts to read beyond allocated memory boundaries, leading to segmentation faults and program crashes. This type of vulnerability directly maps to CWE-121, which addresses stack-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read errors. The improper memory handling demonstrates a failure to implement proper input validation and memory boundary checks that are fundamental to secure coding practices.
The operational impact of CVE-2018-5684 extends beyond simple denial of service conditions, as it can be leveraged by remote attackers to disrupt services and potentially gain unauthorized system access. When a victim system processes a maliciously crafted avi file through an application utilizing the vulnerable Libav library, the program will crash due to the segmentation fault caused by the invalid memory copy operation. This vulnerability affects any system that processes avi files through Libav-based applications, including media players, streaming servers, and content management systems. The remote exploitation capability means that attackers can trigger the vulnerability without requiring local access to the target system, making it particularly dangerous for web-based applications and services. From an ATT&CK framework perspective, this vulnerability aligns with the T1203 technique for legitimate program execution, where attackers leverage existing software to perform malicious activities, and represents a potential entry point for more sophisticated attacks through service disruption.
Mitigation strategies for CVE-2018-5684 must focus on immediate software updates and comprehensive input validation measures. The primary remediation involves upgrading to a patched version of Libav where the invalid memcpy operation has been corrected and proper bounds checking has been implemented. Organizations should also implement strict file format validation procedures that reject suspicious or malformed avi files before processing them through multimedia libraries. Additional protective measures include deploying sandboxing mechanisms for multimedia file processing, implementing network-based file filtering to block suspicious content, and establishing robust monitoring systems to detect potential exploitation attempts. Security teams should also consider implementing application whitelisting policies that restrict the execution of multimedia applications to known good versions and monitor for unusual memory access patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper memory management practices and the need for comprehensive testing of input validation mechanisms in multimedia processing libraries to prevent similar issues from occurring in the future.