CVE-2022-22719: Apache HTTP Server DoS Vulnerability

CVE-2022-22719 Overview

CVE-2022-22719 is an Out-of-Bounds Read vulnerability affecting Apache HTTP Server version 2.4.52 and earlier. A carefully crafted request body can cause a read to a random memory area which could cause the process to crash, resulting in a denial of service condition. This vulnerability stems from improper initialization (CWE-665) in the mod_lua module's request body handling.

Critical Impact

This vulnerability allows remote attackers to crash Apache HTTP Server instances through specially crafted HTTP requests, potentially causing significant service disruption for web applications and services relying on the affected server.

Affected Products

• Apache HTTP Server versions up to and including 2.4.52
• Debian Linux 9.0
• Fedora 34, 35, and 36
• Oracle HTTP Server 12.2.1.3.0 and 12.2.1.4.0
• Oracle ZFS Storage Appliance Kit 8.8
• Apple macOS and Mac OS X 10.15.7 (various security update levels)

Discovery Timeline

• 2022-03-14 - CVE-2022-22719 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-22719

Vulnerability Analysis

This vulnerability exists within the mod_lua module of Apache HTTP Server, specifically in how it handles request body content. When processing certain malformed HTTP request bodies, the server performs a read operation from uninitialized or random memory locations. This improper memory access can lead to unpredictable behavior, most commonly resulting in a process crash.

The vulnerability is classified under CWE-665 (Improper Initialization), indicating that the root issue lies in memory not being properly initialized before being accessed. The attack can be executed remotely over the network without requiring authentication or user interaction, making it particularly concerning for internet-facing Apache servers.

Root Cause

The root cause is improper initialization of memory within the mod_lua request body handling code. When the mod_lua module processes request bodies, it fails to properly initialize certain memory regions before reading from them. This uninitialized memory read can access arbitrary memory locations, causing the httpd worker process to crash when it encounters invalid memory addresses or protected memory regions.

Attack Vector

The attack vector for CVE-2022-22719 is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by sending specially crafted HTTP requests to a vulnerable Apache HTTP Server instance that has mod_lua enabled. The malicious request body triggers the improper memory read operation, causing the server process to crash.

The exploitation process involves:

1. Identifying a target Apache HTTP Server with mod_lua enabled
2. Crafting a malicious HTTP request with a specially formatted body
3. Sending the request to the target server
4. The server's mod_lua module processes the request and performs an uninitialized memory read
5. The read from random memory causes the httpd process to crash

Technical details regarding the specific exploitation mechanism can be found in the Openwall OSS-Security Post and the Apache HTTPD Vulnerability List.

Detection Methods for CVE-2022-22719

Indicators of Compromise

• Unexpected Apache httpd child process crashes or restarts in error logs
• Increased frequency of HTTP 500 errors or connection resets
• Unusual patterns in HTTP request bodies targeting Lua-enabled endpoints
• Core dumps or segmentation fault entries in system logs related to httpd processes

Detection Strategies

• Monitor Apache error logs for segmentation faults and unexpected worker process terminations
• Implement Web Application Firewall (WAF) rules to detect malformed request bodies
• Deploy intrusion detection signatures that identify exploitation attempts targeting mod_lua
• Review Apache access logs for suspicious patterns of requests to Lua-enabled endpoints

Monitoring Recommendations

• Configure Apache to log detailed request information including request bodies for forensic analysis
• Set up automated alerts for httpd process crashes or abnormal restart patterns
• Monitor system resource utilization for signs of repeated crash-restart cycles
• Implement centralized log collection to correlate crash events across multiple servers

How to Mitigate CVE-2022-22719

Immediate Actions Required

• Upgrade Apache HTTP Server to version 2.4.53 or later immediately
• If immediate patching is not possible, disable the mod_lua module if it is not required
• Apply vendor-specific patches from Debian, Fedora, Oracle, or Apple as applicable to your environment
• Implement rate limiting and request filtering at the network perimeter to reduce exposure

Patch Information

Apache Software Foundation has released version 2.4.53 which addresses this vulnerability. Organizations should upgrade to this version or later to remediate CVE-2022-22719. For detailed patch information, consult the Apache HTTPD Vulnerability List.

Vendor-specific advisories are available from:

• Oracle April 2022 Security Alerts
• Debian LTS Advisory
• Apple Security Updates
• Gentoo GLSA 202208-20
• NetApp Security Advisory

Workarounds

• Disable the mod_lua module if Lua scripting functionality is not required by commenting out or removing the LoadModule lua_module directive
• Restrict access to Lua-enabled endpoints using Apache's access control directives to limit exposure
• Deploy a reverse proxy or WAF in front of vulnerable Apache instances to filter malicious requests
• Implement network segmentation to limit the attack surface of vulnerable servers

# Disable mod_lua module in Apache configuration
# Edit /etc/apache2/mods-enabled/ or /etc/httpd/conf.modules.d/

# Comment out or remove the following line:
# LoadModule lua_module modules/mod_lua.so

# Alternatively, on Debian/Ubuntu, disable the module:
sudo a2dismod lua

# Restart Apache to apply changes
sudo systemctl restart apache2
# or
sudo systemctl restart httpd