Memory Leak in NGINX JavaScript (njs) via xml.parse()

Executive Summary

NGINX JavaScript (njs) has a vulnerability where the built-in njs engine leaks a libxml2 parser context when xml.parse() fails. The failure path did not register cleanup and the context was not released for the lifetime of the process. An unauthenticated attacker may send requests with malformed XML and can cause unbounded memory growth in long-lived NGINX worker processes.

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Detection Guidance

Detecting this vulnerability requires monitoring for unusual memory usage in NGINX worker processes due to malformed XML parsing. Check for processes consuming excessive memory with commands like 'top', 'htop', or 'ps aux | grep nginx'. Monitor logs for repeated parsing failures or worker terminations in NGINX error logs.

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Impact Analysis

This vulnerability may allow remote attackers to send requests that trigger repeated parsing of malformed XML and may lead to NGINX worker termination or denial of service. There is no control plane exposure; this is a data plane issue only.

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Compliance Impact

This vulnerability causes unbounded memory growth in NGINX worker processes due to malformed XML parsing failures, which may lead to denial of service. This could impact compliance with standards like GDPR or HIPAA by disrupting availability of services handling personal or health data.

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Mitigation Strategies

Immediately update NGINX JavaScript (njs) to the latest patched version. If updating is not possible, disable the xml.parse() function in njs configurations or restrict XML parsing in NGINX configurations. Restart NGINX to clear leaked contexts and monitor for continued issues.

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