CVE-2017-8313 in VLC
Summary
by MITRE
Heap out-of-bound read in ParseJSS in VideoLAN VLC before 2.2.5 due to missing check of string termination allows attackers to read data beyond allocated memory and potentially crash the process via a crafted subtitles file.
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Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2017-8313 represents a critical heap out-of-bound read flaw within the ParseJSS component of VideoLAN VLC media player version 2.2.4 and earlier. This issue stems from insufficient validation of string termination within the JavaScript subtitle parsing functionality, creating a scenario where maliciously crafted subtitle files can trigger unauthorized memory access patterns. The vulnerability specifically affects the processing of JavaScript subtitles used in video playback, where the parser fails to properly verify string boundaries before reading data from allocated heap memory. The absence of proper bounds checking in the string handling logic allows attackers to construct specially formatted subtitle files that cause the parser to read beyond the intended memory boundaries, potentially exposing sensitive data from adjacent memory regions.
The technical exploitation of this vulnerability occurs when VLC processes a maliciously crafted subtitle file containing malformed JavaScript content. During the parsing operation, the ParseJSS function attempts to read string data without verifying that the string has proper termination characters, leading to memory access violations that extend beyond allocated buffer limits. This flaw manifests as a heap-based out-of-bounds read condition that can result in information disclosure, system instability, or potential process crashes. The vulnerability is particularly concerning because it operates within the media player's subtitle processing pipeline, which is commonly used during normal video playback operations, making it accessible through routine user interactions with media content. The memory corruption resulting from this out-of-bounds read can expose sensitive information stored in adjacent memory locations, potentially including cryptographic keys, user credentials, or other confidential data that may be stored in the same memory segments.
From an operational perspective, this vulnerability presents significant security implications for users who may encounter malicious subtitle files in video content, particularly in scenarios involving untrusted media sources or when downloading content from third-party providers. The impact extends beyond simple denial of service, as the out-of-bound memory reads can potentially expose confidential information stored in memory, creating data leakage risks that align with common attack patterns described in the attack technique framework. The vulnerability's classification under CWE-125 indicates it falls within the category of out-of-bounds read conditions, while its exploitation path through media player components connects to broader ATT&CK tactics including privilege escalation and information gathering. The attack surface is particularly wide given that subtitle files are often automatically processed during video playback without user intervention, making this vulnerability exploitable through passive means.
Mitigation strategies for CVE-2017-8313 primarily focus on immediate software updates to VLC version 2.2.5 or later, which contain the necessary patches to address the string termination validation issue. Organizations should implement comprehensive patch management procedures to ensure all VLC installations are updated promptly, particularly in environments where users may encounter untrusted media content. Additional defensive measures include implementing strict file validation policies for subtitle files, disabling automatic subtitle loading in high-security environments, and deploying network-based intrusion detection systems that can identify suspicious subtitle file patterns. The vulnerability also highlights the importance of input validation and memory safety practices in multimedia processing components, aligning with security best practices outlined in various cybersecurity frameworks. Users should exercise caution when downloading or opening subtitle files from untrusted sources, as the vulnerability can be exploited through social engineering attacks that deliver malicious subtitle content disguised as legitimate media attachments.