CVE-2017-8311 in VLC
Summary
by MITRE
Potential heap based buffer overflow in ParseJSS in VideoLAN VLC before 2.2.5 due to skipping NULL terminator in an input string allows attackers to execute arbitrary code via a crafted subtitles file.
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Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2017-8311 represents a critical heap-based buffer overflow flaw within the ParseJSS component of VideoLAN VLC media player versions prior to 2.2.5. This vulnerability arises from improper handling of input strings during subtitle file processing, specifically when parsing javascript-based subtitle files. The flaw manifests when the parser skips the NULL terminator during string processing, creating conditions where attacker-controlled data can overflow allocated heap memory buffers. This vulnerability falls under the CWE-121 heap-based buffer overflow category, which is classified as a serious memory safety issue that can lead to arbitrary code execution. The ATT&CK framework categorizes this as a code injection technique under the T1059.007 sub-technique, specifically targeting application-level vulnerabilities in multimedia processing components. The vulnerability is particularly concerning because it can be exploited through crafted subtitle files that are commonly used in multimedia presentations, making it accessible to attackers who can influence the content of media files played by vulnerable VLC versions.
The technical implementation of this vulnerability involves the ParseJSS function within VLC's subtitle parsing subsystem where input strings are processed without proper bounds checking. When a maliciously crafted subtitle file is loaded, the parser fails to account for the proper string termination during memory allocation, leading to memory corruption that can be leveraged for code execution. The heap overflow occurs because the application allocates memory based on the length of the input string but does not properly account for the missing NULL terminator in its calculations. This creates a situation where additional data can be written beyond the allocated buffer boundaries, potentially overwriting adjacent memory structures including return addresses and function pointers. The vulnerability is particularly dangerous because it requires minimal user interaction - simply opening a malicious subtitle file within VLC is sufficient to trigger the exploit, making it a prime candidate for drive-by attacks or social engineering campaigns targeting multimedia content.
The operational impact of CVE-2017-8311 extends beyond simple code execution as it represents a complete compromise of the affected system. Attackers who successfully exploit this vulnerability can gain full control over the target machine, potentially leading to data theft, system monitoring, or further network infiltration. The vulnerability affects all platforms where VLC is installed, including Windows, macOS, and Linux systems, making it a widespread concern for organizations and individual users alike. The exploitability of this vulnerability is enhanced by the fact that subtitle files are commonly used in multimedia presentations, movies, and educational content, providing numerous attack vectors for threat actors. Security researchers have noted that this vulnerability demonstrates poor input validation practices in multimedia processing libraries, which is consistent with the broader class of issues found in legacy multimedia frameworks. The vulnerability's impact is further amplified by the fact that VLC is widely distributed and used across multiple operating systems, creating a large attack surface that makes this vulnerability particularly attractive to threat actors.
Mitigation strategies for CVE-2017-8311 center on immediate software updates to VLC version 2.2.5 or later, which contain the necessary patches to address the heap overflow condition. Organizations should implement strict file validation policies that prevent execution of untrusted subtitle files, particularly those with javascript extensions. Network administrators should consider implementing content filtering solutions that can detect and block potentially malicious subtitle files in enterprise environments. The security community has recommended that users avoid opening subtitle files from untrusted sources and that administrators regularly audit their VLC installations to ensure they are running patched versions. Additional defensive measures include implementing application whitelisting policies that restrict VLC execution to trusted environments and monitoring for suspicious file access patterns. The vulnerability highlights the importance of proper input validation and memory management practices in multimedia applications, which aligns with security best practices outlined in the OWASP Top Ten and NIST cybersecurity guidelines. System administrators should also consider deploying intrusion detection systems that can identify exploitation attempts targeting multimedia processing components, as this vulnerability can be used as part of broader attack campaigns targeting media player applications.