CVE-2017-7206 in libav
Summary
by MITRE
The ff_h2645_extract_rbsp function in libavcodec in libav 9.21 allows remote attackers to cause a denial of service (heap-based 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-2017-7206 represents a critical heap-based buffer over-read flaw within the ff_h2645_extract_rbsp function of libavcodec library version 9.21. This issue resides in the handling of h264 video streams where the function fails to properly validate input data before processing, creating a scenario where maliciously crafted video files can trigger unexpected memory access patterns. The vulnerability specifically affects the decoding process of h264 video content and demonstrates how improper bounds checking can lead to memory corruption issues that impact the stability and security of multimedia processing applications.
The technical implementation of this vulnerability stems from insufficient input validation within the rbsp (raw byte sequence payload) extraction routine that processes h264 video data. When processing specially crafted h264 files, the function attempts to read beyond allocated heap memory boundaries, potentially causing either a denial of service condition where the application crashes due to invalid memory access or more sinisterly, allows attackers to read sensitive data from adjacent memory locations. This behavior aligns with CWE-125, which describes out-of-bounds read vulnerabilities, and demonstrates how buffer over-read conditions can be exploited for information disclosure attacks. The flaw operates at the codec level where video data is parsed and decoded, making it particularly dangerous as it can be triggered simply by opening or processing a malicious video file.
From an operational impact perspective, this vulnerability creates significant risks for multimedia applications, streaming services, and content delivery platforms that rely on libav for video processing. Attackers can exploit this flaw to cause service disruption through denial of service attacks, making legitimate video content inaccessible to users, or potentially extract confidential information from process memory such as encryption keys, user credentials, or proprietary data. The vulnerability affects systems where h264 video processing occurs, including media servers, content management systems, and any application that handles video file decoding. The attack vector requires only that a victim process a maliciously crafted h264 file, making it particularly dangerous in automated processing environments where files are automatically decoded and analyzed. This vulnerability can be leveraged in combination with other attack techniques to achieve broader system compromise, potentially aligning with ATT&CK technique T1059 for execution through multimedia processing and T1068 for privilege escalation via application vulnerabilities.
Mitigation strategies for CVE-2017-7206 primarily focus on immediate software updates and patches to the affected libav library versions. System administrators should prioritize upgrading to patched versions of libavcodec that address the buffer over-read condition in the ff_h2645_extract_rbsp function. Additionally, implementing input validation measures at the application level can provide defense-in-depth protection, including sanitizing video file inputs before processing and employing memory protection mechanisms such as stack canaries and address space layout randomization. Network-level filtering can also help by blocking suspicious video content or implementing strict content validation protocols for multimedia files. Organizations should also consider deploying intrusion detection systems that can identify potential exploitation attempts targeting this specific vulnerability pattern, as well as implementing regular security assessments of multimedia processing pipelines to identify similar buffer overflow conditions. The remediation process should include comprehensive testing of patched libraries to ensure that the fix does not introduce regressions in video processing functionality while maintaining the security improvements necessary to prevent exploitation.