CVE-2017-7208 in libav
Summary
by MITRE
The decode_residual function in libavcodec in libav 9.21 allows remote attackers to cause a denial of service (buffer over-read) or obtain sensitive information from process memory via a crafted h264 video file.
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Analysis
by VulDB Data Team • 09/10/2020
The vulnerability identified as CVE-2017-7208 resides within the decode_residual function of libavcodec library version 9.21 which is part of the broader libav multimedia framework. This critical flaw manifests as a buffer over-read condition that can be exploited by remote attackers through the careful crafting of h264 video files. The issue stems from inadequate input validation and bounds checking within the video decoding process, specifically when handling residual data components that are essential for reconstructing video frames during decompression. The vulnerability affects the core decoding functionality that processes h264 video streams, making it a significant threat to any system that handles video content processing or streaming.
The technical implementation of this vulnerability involves the decode_residual function failing to properly validate the size and boundaries of residual data blocks within h264 video frames. When a maliciously crafted h264 file is processed, the function attempts to read beyond the allocated memory boundaries, potentially accessing adjacent memory regions that contain sensitive data or causing the application to crash. This buffer over-read condition can be leveraged to either trigger a denial of service by causing application crashes or to extract information from process memory that may contain confidential data such as cryptographic keys, user credentials, or system information. The flaw operates at the intersection of multimedia processing and memory safety, making it particularly dangerous in environments where video decoding is performed on untrusted content.
The operational impact of CVE-2017-7208 extends beyond simple service disruption to include potential information disclosure risks that could compromise system security. Systems utilizing affected versions of libavcodec are vulnerable to attacks where remote adversaries can craft malicious h264 files to either crash applications or extract sensitive information from memory. This vulnerability affects a wide range of applications that depend on libav for video processing including media players, streaming servers, content management systems, and multimedia applications. The remote nature of the attack means that exploitation can occur without requiring local access to the target system, making it particularly concerning for web-based applications and services that process user-uploaded video content. The vulnerability aligns with CWE-125 which describes out-of-bounds read conditions, and represents a classic example of how multimedia processing libraries can become attack vectors when proper input validation is absent.
Mitigation strategies for CVE-2017-7208 primarily focus on immediate software updates and patches to the affected libavcodec library. System administrators should prioritize upgrading to patched versions of libav or alternative multimedia frameworks that address this vulnerability. Additionally, implementing input validation measures at the application level can provide defense-in-depth protection by sanitizing video content before processing or by employing sandboxing techniques to limit the impact of potential exploitation. Network-based mitigations such as content filtering and media validation can help prevent malicious h264 files from reaching vulnerable applications. The ATT&CK framework categorizes this vulnerability under the T1203 technique for Obfuscated Files or Information, as attackers may use crafted video files to bypass security controls. Organizations should also consider implementing monitoring and detection mechanisms to identify potential exploitation attempts through unusual memory access patterns or application crashes. Given the nature of the vulnerability, regular security assessments of multimedia processing components and maintaining updated security patches form essential defensive measures against this type of buffer over-read attack.