Uninitialized Memory Access in NGINX Plus and Open Source

Executive Summary

This vulnerability affects NGINX Plus and NGINX Open Source when the slice directive and unnamed regex captures are configured or during a background cache update. It allows unauthenticated attackers to send requests that cause uninitialized memory access in the NGINX worker process, potentially leading to limited memory disclosure or a worker process restart.

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Detection Guidance

Detecting this vulnerability requires checking if the ngx_http_slice_module is enabled in your NGINX configuration. Use the command 'nginx -V 2>&1 | grep -o with-http_slice_module' to verify if the module is compiled. If it returns 'with-http_slice_module', the module is active. Additionally, inspect your NGINX configuration files for the 'slice' directive or unnamed regex captures.

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Impact Analysis

This vulnerability allows remote attackers to potentially access sensitive memory contents or cause NGINX worker processes to restart unexpectedly. This could disrupt services relying on NGINX, though it does not provide full control over the system.

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Compliance Impact

This vulnerability may lead to limited disclosure of memory contents, which could potentially expose sensitive data. This could impact compliance with GDPR (data protection) and HIPAA (health information privacy) if such data is involved. However, the vulnerability does not provide direct control over data or systems, limiting its immediate regulatory impact.

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Mitigation Strategies

If the ngx_http_slice_module is enabled, disable it by recompiling NGINX without the --with-http_slice_module flag. Remove any 'slice' directives or unnamed regex captures from your configuration files. Restart NGINX to apply changes. Ensure you are running a patched version of NGINX once available.

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