CVE-2018-5766 in libav
Summary
by MITRE
In Libav through 12.2, there is an invalid memcpy in the av_packet_ref function of libavcodec/avpacket.c. Remote attackers could leverage this vulnerability to cause a denial of service (segmentation fault) via a crafted avi file.
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Analysis
by VulDB Data Team • 02/02/2023
The vulnerability identified as CVE-2018-5766 represents a critical memory corruption flaw within the Libav multimedia framework version 12.2 and earlier. This issue manifests in the av_packet_ref function located within the libavcodec/avpacket.c source file, where an invalid memcpy operation occurs during packet reference handling. The flaw specifically affects the processing of AVI container files, making it particularly dangerous for multimedia applications that handle user-provided content. The vulnerability stems from inadequate input validation and memory management within the packet reference mechanism, creating a condition where malformed data can trigger unexpected behavior in the underlying memory operations.
The technical exploitation of this vulnerability occurs when a remote attacker crafts a malicious AVI file that triggers the flawed memcpy operation during packet reference processing. When the Libav library attempts to copy memory segments in the av_packet_ref function, the invalid memory copy operation leads to a segmentation fault that crashes the application. This denial of service condition can be reliably triggered through crafted input without requiring special privileges or complex attack vectors. The vulnerability specifically impacts the memory management subsystem of Libav, where the memcpy function receives invalid parameters or attempts to access memory regions that are either unmapped or insufficiently allocated, resulting in the application termination.
From an operational perspective, this vulnerability poses significant risks to multimedia applications that rely on Libav for video and audio processing. Systems processing untrusted AVI files, including media servers, content management platforms, and streaming services, become vulnerable to denial of service attacks that can disrupt service availability. The impact extends beyond simple application crashes to potentially affect entire service infrastructures, as attackers can repeatedly exploit this vulnerability to maintain service disruption. The vulnerability's remote exploitation capability means that systems processing AVI content over network connections are at risk, making it particularly dangerous for web applications and media processing services that accept user uploads.
Security mitigations for CVE-2018-5766 involve immediate software updates to Libav versions that contain the patched av_packet_ref function with proper memory validation and bounds checking. Organizations should implement input validation measures that sanitize AVI file content before processing, including size validation, format verification, and content scanning for suspicious patterns. The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and represents a memory safety issue that can be addressed through proper bounds checking and input validation. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique for network denial of service attacks, where adversaries leverage software flaws to disrupt service availability. System administrators should also consider implementing network segmentation and monitoring to detect potential exploitation attempts, while application developers should review their Libav integration for proper error handling and resource management to prevent similar issues in custom implementations.