Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-33483 is a high-severity vulnerability in the WWBN AVideo platform, specifically in the aVideoEncoderChunk.json.php endpoint in versions up to 26.0. This endpoint is a standalone PHP script that lacks authentication, framework integration, and resource limits.'}, {'type': 'paragraph', 'content': "An unauthenticated remote attacker can send arbitrary POST data to this endpoint, which writes the data to temporary files in the server's /tmp/ directory without any size cap, rate limiting, or cleanup mechanism. This allows attackers to create unlimited large temporary files, leading to disk space exhaustion."}, {'type': 'paragraph', 'content': 'The accumulation of these files can cause denial of service (DoS) for the entire server by exhausting disk space, which affects PHP session handling, MySQL temp tables, and other system services relying on the /tmp/ directory.'}] [2]

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Impact Analysis

This vulnerability can lead to a denial of service (DoS) condition on the affected server by exhausting disk space in the /tmp/ directory.

• Attackers can create unlimited large temporary files without authentication or user interaction.
• Disk space exhaustion causes cascading failures such as broken PHP session handling, failed MySQL temporary tables, and crashing of system services that rely on tmpfs.
• The vulnerability can be exploited remotely and even via cross-origin requests, allowing attackers to leverage victim browsers as distributed attack vectors.
• Temporary files persist indefinitely without cleanup, meaning even short attacks have lasting effects until manual intervention.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by monitoring the presence and size of temporary files created by the vulnerable script in the /tmp/ directory. Specifically, look for files prefixed with "YTPChunk_" which are created by the aVideoEncoderChunk.json.php endpoint.'}, {'type': 'list_item', 'content': 'Check for existing temporary chunk files: ls -lh /tmp/YTPChunk_*'}, {'type': 'list_item', 'content': 'Monitor disk usage to detect abnormal growth in /tmp/: du -sh /tmp/'}, {'type': 'list_item', 'content': 'Use network monitoring or web server logs to identify repeated or large POST requests to the aVideoEncoderChunk.json.php endpoint.'}, {'type': 'list_item', 'content': 'Example command to detect large POST requests (assuming Apache logs): grep "POST /objects/aVideoEncoderChunk.json.php" /var/log/apache2/access.log | awk \'{print $0}\''}] [2]

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Mitigation Strategies

Immediate mitigation steps include limiting the impact of the vulnerability by cleaning up existing temporary files and restricting upload sizes.

• Manually delete existing temporary chunk files to free disk space: rm -f /tmp/YTPChunk_*
• Implement a cleanup mechanism such as a cron job to regularly remove old YTPChunk_* files (e.g., files older than 1 hour).
• Apply the patch from commit 33d1bae6c731ef1682fcdc47b428313be073a5d1 which enforces upload size limits, cleans up orphaned chunk files, and rejects oversized uploads with HTTP 413 errors.
• Restrict access to the vulnerable endpoint by adding authentication checks or limiting access via firewall or web server configuration.

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