CVE-2017-8310 in VLC
Summary
by MITRE
Heap out-of-bound read in CreateHtmlSubtitle in VideoLAN VLC 2.2.x due to missing check of string termination allows attackers to read data beyond allocated memory and potentially crash the process (causing a denial of service) via a crafted subtitles file.
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Analysis
by VulDB Data Team • 05/24/2017
The vulnerability identified as CVE-2017-8310 represents a critical heap out-of-bounds read condition within the VideoLAN VLC media player version 2.2.x series. This flaw exists in the CreateHtmlSubtitle function which processes subtitle files, specifically targeting the handling of string termination checks during memory allocation. The vulnerability stems from insufficient validation of input data within the subtitle parsing mechanism, creating a scenario where attacker-controlled data can cause the application to read memory beyond its allocated boundaries. This particular issue demonstrates a classic memory safety vulnerability that has significant implications for media player security and can be exploited through maliciously crafted subtitle files.
The technical implementation of this vulnerability occurs when VLC processes HTML-based subtitle files containing specially crafted data structures. During the parsing process, the CreateHtmlSubtitle function fails to properly validate string termination before performing memory operations, leading to a situation where the application attempts to read beyond the allocated heap memory region. This out-of-bounds read can potentially expose sensitive data from adjacent memory locations or cause the application to crash due to invalid memory access patterns. The vulnerability is particularly concerning because it operates within the legitimate processing path of subtitle handling, making it difficult to distinguish between normal and malicious input without proper validation.
From an operational perspective, this vulnerability creates a denial of service condition that can be reliably triggered by an attacker who controls the subtitle content. The heap out-of-bounds read can lead to unpredictable application behavior including crashes, memory corruption, or potentially information disclosure depending on the memory layout at the time of access. The attack vector is relatively simple as it only requires the victim to play a media file with a crafted subtitle file, making it a particularly dangerous vulnerability in environments where users might encounter untrusted media content. The impact extends beyond simple service disruption as the vulnerability could potentially be leveraged in more sophisticated attacks depending on the specific memory conditions and application context.
Security mitigations for CVE-2017-8310 should focus on implementing proper input validation and bounds checking within the subtitle parsing routines. The most effective approach involves adding comprehensive string termination checks before any memory operations occur, ensuring that all input data is properly validated and sanitized. Organizations should prioritize updating to patched versions of VLC media player where the vulnerability has been addressed through proper bounds checking mechanisms. Additionally, implementing application sandboxing and memory protection techniques can provide additional defense-in-depth measures. This vulnerability aligns with CWE-125 Out-of-bounds Read and can be mapped to ATT&CK technique T1203 Exploitation for Client Execution, highlighting the importance of input validation in preventing remote code execution through media processing components. The remediation process should include thorough code review of similar functions within the application to identify and address potential analogous vulnerabilities in the subtitle processing pipeline.