CVE-2016-9825 in libav
Summary
by MITRE
libswscale/utils.c in libav 11.8 allows remote attackers to cause a denial of service (crash) via vectors involving left shift of a negative value.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 09/03/2020
The vulnerability identified as CVE-2016-9825 resides within the libswscale/utils.c component of the libav library version 11.8, representing a critical security flaw that enables remote attackers to execute denial of service attacks through carefully crafted input vectors. This issue specifically manifests when the software processes left shift operations on negative values, a condition that can lead to unexpected behavior and system instability. The libav library serves as a fundamental multimedia processing framework that handles various audio and video encoding and decoding tasks across numerous applications and systems, making this vulnerability particularly concerning for widespread impact.
The technical root cause of this vulnerability stems from improper input validation and arithmetic handling within the libswscale utility functions. When the software encounters negative values during left shift operations, the underlying implementation fails to properly handle the sign extension behavior that should occur during such mathematical operations. This flaw falls under the CWE-129 weakness category, which specifically addresses issues related to improper handling of input values that can lead to unexpected arithmetic results. The vulnerability demonstrates characteristics consistent with integer overflow and underflow conditions, where the negative value processing during bit manipulation operations creates unpredictable outcomes that can trigger system crashes.
From an operational perspective, this vulnerability creates significant risk for systems that rely on libav for multimedia processing, particularly those exposed to untrusted input streams such as web applications, media servers, and content management systems. Attackers can exploit this weakness by providing maliciously crafted media files or stream parameters that trigger the vulnerable code path during the scaling or conversion processes. The denial of service impact extends beyond simple application crashes to potentially affect entire service availability, as the affected systems may become unresponsive or require manual restart to recover. This vulnerability is particularly dangerous in server environments where continuous availability is critical, as it can be exploited to disrupt legitimate service operations without requiring elevated privileges or complex attack chains.
The exploitation of CVE-2016-9825 aligns with several tactics described in the MITRE ATT&CK framework, specifically within the privilege escalation and denial of service categories. The attack vector involves manipulating input parameters to trigger unexpected behavior in the target software, which represents a common technique for achieving system compromise. Organizations should consider this vulnerability as part of their broader security posture assessment, particularly in environments where multimedia processing services are exposed to external networks. The vulnerability's impact is amplified when considering that many modern applications rely on libav or its derivatives for handling multimedia content, creating a wide attack surface that extends across various software ecosystems including web browsers, media players, and content delivery platforms.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected libav installations to the latest available versions that contain the necessary code fixes. System administrators should implement network segmentation and input validation controls to limit exposure to potentially malicious media content, while also monitoring for unusual system behavior that might indicate exploitation attempts. The remediation process should include comprehensive testing of patched environments to ensure that the fix does not introduce regressions in multimedia processing functionality, as the libswscale component is integral to many video processing workflows. Additionally, organizations should conduct thorough vulnerability assessments across their software stacks to identify other potential dependencies on vulnerable libav versions, as this particular flaw may exist in various derivative libraries and applications that utilize the affected code base.