Memory Exhaustion in exceljs-hardened via Malicious XLSX

Executive Summary

This vulnerability affects exceljs-hardened versions before 5.0.0. It allows attackers to upload specially crafted Excel files that are highly compressed. When these files are decompressed in memory, they expand significantly, consuming large amounts of system resources and causing denial of service by exhausting available memory.

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Detection Guidance

Monitor for processes consuming excessive memory when handling Excel files. Check for unusually large memory usage spikes in applications using exceljs or exceljs-hardened versions below 5.0.0. Use system monitoring tools like top, htop, or ps to observe memory consumption during file processing.

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Impact Analysis

If you process untrusted Excel files using vulnerable versions of exceljs or exceljs-hardened, a single malicious file could crash your application or server by consuming all available memory. This leads to service outages and potential system instability.

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Compliance Impact

This vulnerability primarily impacts system availability by causing denial of service through memory exhaustion. While it does not directly violate GDPR or HIPAA, it could lead to service disruptions that may affect compliance with availability requirements in these regulations. GDPR requires data availability controls (Article 32) and HIPAA requires safeguards against unauthorized access or disruption (Security Rule). A DoS condition could hinder access to protected health information or personal data, potentially violating these standards.

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Mitigation Strategies

Upgrade to exceljs-hardened version 5.0.0 or later which enforces resource limits. If upgrading is not possible, avoid processing untrusted Excel files or run the application in a memory-limited container. Implement file size checks before decompression to reject oversized files.

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