Denial of Service in Netty Redis Codec

Executive Summary

This vulnerability exists in the netty-codec-redis component of the Netty framework prior to versions 4.1.135.Final and 4.2.15.Final. An attacker can exploit it by sending specially crafted Redis payloads across multiple connections that lack the required '\r\n' sequence. This causes the server's direct memory pool to be exhausted, resulting in an OutOfDirectMemoryError.

As a result, the server is unable to process legitimate connections, effectively causing a denial of service (DoS).

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Impact Analysis

The primary impact of this vulnerability is a denial of service (DoS) condition. By exhausting the server's direct memory pool, legitimate users are prevented from establishing connections or using the service.

This can lead to service outages, degraded performance, and potential disruption of business operations that rely on the affected Netty-based Redis services.

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Mitigation Strategies

To mitigate this vulnerability, upgrade netty-codec-redis to version 4.1.135.Final or 4.2.15.Final or later, as these versions contain the patch that prevents the denial of service caused by crafted Redis payloads.

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Compliance Impact

This vulnerability causes a denial of service (DoS) by exhausting the server's direct memory pool, which prevents legitimate connections from being processed.

However, there is no information provided about any impact on data confidentiality, integrity, or privacy that would directly affect compliance with standards such as GDPR or HIPAA.

Therefore, based on the available information, this vulnerability primarily affects availability but does not explicitly indicate compliance issues with common regulations.

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Detection Guidance

This vulnerability can be detected by monitoring for unusual or excessive direct memory usage in the Netty-based Redis server, especially looking for OutOfDirectMemoryError crashes.

Since the attack involves sending crafted Redis payloads without proper line terminators (\r\n) across multiple connections, network traffic analysis tools can be used to detect such malformed Redis commands.

Suggested commands to detect potential exploitation attempts include:

• Using tcpdump or Wireshark to capture Redis traffic and filter for payloads missing the \r\n sequence.
• Example tcpdump command: tcpdump -i <interface> -A port 6379 | grep -v '\r\n'
• Monitoring application logs for OutOfDirectMemoryError exceptions indicating direct memory exhaustion.
• Using JVM monitoring tools (like jstat or VisualVM) to observe direct memory usage spikes in the Netty process.

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