HTTP/2 SETTINGS_MAX_FRAME_SIZE Zero Value Infinite Loop in Go

Executive Summary

This vulnerability occurs in the Go programming language's HTTP/2 transport implementation. When processing HTTP/2 SETTINGS frames, if the transport receives a SETTINGS_MAX_FRAME_SIZE value of 0, it enters an infinite loop of writing CONTINUATION frames.

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Impact Analysis

The infinite loop of writing CONTINUATION frames caused by this vulnerability can lead to a denial-of-service (DoS) condition. A malicious server could exploit this to disrupt the normal operation of a client using the affected Go HTTP/2 transport.

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Detection Guidance

This vulnerability occurs when an HTTP/2 SETTINGS frame contains a SETTINGS_MAX_FRAME_SIZE value of 0, causing the transport to enter an infinite loop of writing CONTINUATION frames.

To detect this on your network or system, you can monitor HTTP/2 traffic for SETTINGS frames with a SETTINGS_MAX_FRAME_SIZE set to 0.

Using network packet capture tools like tcpdump or Wireshark, you can filter HTTP/2 SETTINGS frames and inspect the SETTINGS_MAX_FRAME_SIZE parameter.

• Example tcpdump command to capture HTTP/2 traffic: tcpdump -i <interface> -w capture.pcap 'tcp port 443'
• Use Wireshark to open the capture and filter for HTTP/2 SETTINGS frames, then check for SETTINGS_MAX_FRAME_SIZE with value 0.

Additionally, monitoring for abnormal continuous CONTINUATION frames being sent by the client could indicate the infinite loop condition.

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Mitigation Strategies

Immediate mitigation involves updating the Go standard library to a version that includes the fix for this vulnerability.

The fix validates the SETTINGS_MAX_FRAME_SIZE value to ensure it is not zero, preventing the infinite loop condition.

If updating is not immediately possible, consider implementing network-level protections to block or filter HTTP/2 SETTINGS frames with invalid SETTINGS_MAX_FRAME_SIZE values.

Monitoring and rate-limiting suspicious HTTP/2 traffic may also help mitigate denial-of-service attempts exploiting this vulnerability.

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Compliance Impact

The provided information does not specify any direct impact of this vulnerability on compliance with common standards and regulations such as GDPR or HIPAA.

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