CVE-2017-11684 in libav
Summary
by MITRE
There is an illegal address access in the build_table function in libavcodec/bitstream.c of Libav 12.1 that will lead to remote denial of service via crafted input.
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Analysis
by VulDB Data Team • 08/25/2025
The vulnerability identified as CVE-2017-11684 represents a critical security flaw within the Libav multimedia framework version 12.1, specifically within the build_table function located in libavcodec/bitstream.c. This issue manifests as an illegal address access condition that can be exploited remotely through the careful crafting of input data. The vulnerability stems from insufficient bounds checking and memory validation within the bitstream parsing logic that processes multimedia content. When maliciously formatted data is processed by the affected Libav library, the build_table function fails to properly validate memory access patterns, leading to unpredictable behavior that can result in system instability.
The technical implementation of this vulnerability involves a classic buffer over-read scenario where the build_table function attempts to access memory locations beyond the allocated buffer boundaries. This occurs during the parsing of bitstream data structures used in multimedia codecs, particularly when handling compressed video or audio content. The flaw operates at the intersection of input validation and memory management, where the function does not adequately verify the size or structure of incoming data before attempting to process it. This type of vulnerability is categorized under CWE-125 as an out-of-bounds read, which is a common vector for denial of service attacks in multimedia processing libraries. The improper handling of memory access patterns creates an opportunity for attackers to manipulate the program flow through carefully constructed input sequences that trigger the vulnerable code path.
From an operational perspective, this vulnerability presents a significant risk to systems that utilize Libav for multimedia processing, including media servers, content delivery networks, and applications that handle user-provided media files. The remote denial of service aspect means that attackers can potentially disrupt services without requiring local system access, making this particularly dangerous in networked environments. The impact extends beyond simple service disruption, as the vulnerability can be exploited to cause application crashes, memory corruption, or even system instability that may lead to more severe consequences. The attack vector is particularly concerning because it can be triggered through legitimate media processing workflows, meaning that any system accepting multimedia input is potentially vulnerable. This vulnerability aligns with ATT&CK technique T1499.004 for network denial of service, as it enables remote exploitation that can render systems unavailable to legitimate users.
The mitigation strategy for CVE-2017-11684 requires immediate patching of the Libav library to version 12.2 or later, which contains the necessary fixes for the memory access validation issues. Organizations should implement comprehensive input validation measures that include bounds checking and proper error handling for all multimedia content processing pipelines. Network segmentation and input filtering should be implemented to reduce the attack surface and limit potential exploitation. Security monitoring should be enhanced to detect unusual patterns of media processing that might indicate exploitation attempts. Additionally, system administrators should consider implementing application-level firewalls or content filtering mechanisms that can prevent malformed media files from reaching the vulnerable processing components. The fix addresses the underlying memory management flaw by introducing proper bounds checking and ensuring that all memory accesses within the build_table function are validated against the actual size of available buffers. This vulnerability demonstrates the critical importance of proper input validation in multimedia processing libraries and the potential for remote exploitation in widely used open source components.