CVE-2019-9746 in libwebm
Summary
by MITRE
In libwebm before 2019-03-08, a NULL pointer dereference caused by the functions OutputCluster and OutputTracks in webm_info.cc will trigger an abort, which allows a DoS attack, a similar issue to CVE-2018-19212.
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability identified as CVE-2019-9746 represents a critical null pointer dereference flaw within the libwebm library, specifically affecting versions prior to 2019-03-08. This issue manifests in the webm_info.cc source file where the functions OutputCluster and OutputTracks exhibit problematic behavior when processing malformed or specially crafted webm files. The vulnerability stems from insufficient input validation and error handling mechanisms that fail to properly check for null pointer conditions before attempting to dereference pointers during the processing of webm container structures. The flaw creates a scenario where an attacker can craft malicious webm files that, when processed by applications using the vulnerable libwebm library, will cause the application to terminate abruptly through an abort signal.
The technical implementation of this vulnerability operates through the manipulation of webm file structures that trigger the execution path containing the null pointer dereference. When the OutputCluster and OutputTracks functions encounter unexpected or malformed data within the webm container, they fail to validate pointer references before attempting to access memory locations. This failure directly violates the principles of secure programming practices and creates a predictable crash condition that can be reliably exploited by adversaries. The vulnerability's classification aligns with CWE-476 which specifically addresses NULL pointer dereference issues, making it a clear example of improper null pointer handling in security-critical code components. The behavior demonstrates characteristics consistent with the attack pattern described in the ATT&CK framework under the T1499.004 sub-technique related to network denial of service attacks through application vulnerabilities.
The operational impact of this vulnerability extends beyond simple application crashes, creating significant risks for systems that rely on libwebm for webm file processing. Applications using the vulnerable library, including media players, content management systems, and streaming services, become susceptible to denial of service attacks where adversaries can remotely cause service interruption by uploading or transmitting malicious webm files. The exploitability of this vulnerability is particularly concerning because it requires minimal sophistication from attackers, making it a preferred target for automated exploitation campaigns. The DoS condition affects not only individual application instances but can potentially compromise entire service availability, especially when multiple applications within a system are vulnerable to the same flaw. The similarity to CVE-2018-19212 indicates a pattern of implementation weaknesses within the libwebm library's processing logic that requires comprehensive code review and remediation efforts to address underlying architectural issues.
Mitigation strategies for CVE-2019-9746 primarily involve immediate patching of the libwebm library to version 2019-03-08 or later, which contains the necessary fixes to properly handle null pointer conditions in the affected functions. Organizations should implement network segmentation and input validation controls to prevent unauthorized users from submitting potentially malicious webm files to systems that utilize the vulnerable library. Additionally, deploying intrusion detection systems that can identify suspicious file upload patterns and implementing application-level sandboxing for media processing operations can provide additional layers of defense. The fix for this vulnerability demonstrates the importance of proper error handling and defensive programming practices, particularly in libraries that process untrusted input data. System administrators should also consider monitoring for abnormal application termination patterns and implement robust logging mechanisms to detect potential exploitation attempts. Regular security assessments and dependency updates form essential components of a comprehensive mitigation strategy that addresses both current vulnerabilities and prevents similar issues from arising in future library versions.