CVE-2024-31079: F5 Nginx Open Source DOS Vulnerability

CVE-2024-31079 Overview

CVE-2024-31079 is a stack-based buffer overflow and out-of-bounds write vulnerability affecting NGINX Plus and NGINX OSS when configured to use the HTTP/3 QUIC module. Undisclosed HTTP/3 requests can cause NGINX worker processes to terminate unexpectedly or potentially cause other adverse impacts on the affected system.

Critical Impact

This vulnerability can lead to denial of service through NGINX worker process termination, potentially affecting web application availability for organizations using HTTP/3 QUIC functionality.

Affected Products

• F5 NGINX Open Source (versions with HTTP/3 QUIC module enabled)
• F5 NGINX Plus R30, R30-p1, R30-p2, R31, and R31-p1
• Fedora 39 and Fedora 40 (NGINX packages)

Discovery Timeline

• 2024-05-29 - CVE-2024-31079 published to NVD
• 2025-01-24 - Last updated in NVD database

Technical Details for CVE-2024-31079

Vulnerability Analysis

This vulnerability is classified under CWE-121 (Stack-based Buffer Overflow) and CWE-787 (Out-of-bounds Write). The flaw exists within NGINX's HTTP/3 QUIC module implementation, which handles the modern HTTP/3 protocol over QUIC transport. When processing certain malformed or specially crafted HTTP/3 requests, the NGINX worker process can encounter a memory corruption condition that leads to process termination.

The exploitation window is notably limited by a timing constraint: the malicious request must arrive during the connection draining process. This draining phase occurs when NGINX is gracefully shutting down connections, and the attacker has no direct visibility into when this state occurs, making reliable exploitation challenging.

Root Cause

The root cause stems from improper memory handling within the HTTP/3 QUIC module during connection state transitions. Specifically, a stack-based buffer overflow condition (CWE-121) combined with an out-of-bounds write (CWE-787) can occur when the module processes HTTP/3 requests during the connection draining phase. The vulnerable code path fails to properly validate request data boundaries before writing to stack memory, allowing memory corruption that destabilizes the worker process.

Attack Vector

The attack is network-based and does not require authentication or user interaction. An attacker must send specially crafted HTTP/3 requests to a vulnerable NGINX instance with the QUIC module enabled. The key constraint is timing—the request must coincide with the connection draining process. Since this timing window is not externally observable, the attack has high complexity and limited reliability.

The attacker would need to:

1. Identify a target NGINX server with HTTP/3 QUIC module enabled
2. Send crafted HTTP/3 requests attempting to trigger the vulnerability
3. Time the requests to coincide with connection draining events

Due to the timing dependency and lack of attacker visibility into the connection state, exploitation requires either sustained attack traffic or fortunate timing to achieve worker process termination.

Detection Methods for CVE-2024-31079

Indicators of Compromise

• Unexpected NGINX worker process crashes or restarts appearing in system logs
• Error logs showing memory-related issues during HTTP/3 request processing
• Increased frequency of worker process exited on signal entries in NGINX error logs
• Unusual spikes in HTTP/3 connection errors or terminations

Detection Strategies

• Monitor NGINX error logs for worker process termination events, particularly those correlating with HTTP/3 traffic
• Implement network traffic analysis to detect anomalous HTTP/3 QUIC request patterns
• Configure process monitoring to alert on unexpected NGINX worker restarts
• Review system logs for segmentation faults or memory corruption indicators related to NGINX processes

Monitoring Recommendations

• Enable verbose logging for the HTTP/3 QUIC module during investigation periods
• Set up automated alerting for NGINX worker process crashes exceeding normal baseline
• Implement SentinelOne Singularity Platform for real-time behavioral monitoring of NGINX processes
• Monitor for memory allocation anomalies using system performance tools

How to Mitigate CVE-2024-31079

Immediate Actions Required

• Review NGINX configurations to determine if the HTTP/3 QUIC module is enabled (listen ... quic directive)
• Apply the latest security patches from F5 for NGINX Plus or update NGINX OSS to patched versions
• Consider temporarily disabling HTTP/3 QUIC functionality if patching is not immediately possible
• Implement rate limiting on HTTP/3 connections to reduce potential attack surface

Patch Information

F5 has released security updates addressing this vulnerability. Organizations running affected versions should consult the F5 Technical Article for specific patch guidance and version information. Fedora users should apply the latest package updates through their distribution's package management system as documented in the Fedora Package Announcement.

Workarounds

• Disable HTTP/3 QUIC module by removing or commenting out listen ... quic directives in NGINX configuration
• Implement a Web Application Firewall (WAF) capable of inspecting HTTP/3 traffic for anomalous patterns
• Use load balancers or reverse proxies that can terminate HTTP/3 before reaching vulnerable NGINX instances
• Restrict HTTP/3 access to trusted networks or clients if full external exposure is not required

# Configuration example - Disable HTTP/3 QUIC in NGINX
# Comment out or remove quic parameters from listen directives

# Before (vulnerable configuration):
# listen 443 quic reuseport;
# listen 443 ssl;

# After (mitigated configuration):
listen 443 ssl;
# quic module disabled until patch is applied

# Reload NGINX configuration
nginx -t && nginx -s reload