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:

Identifying a target Apache HTTP Server with mod_lua enabled
Crafting a malicious HTTP request with a specially formatted body
Sending the request to the target server
The server's mod_lua module processes the request and performs an uninitialized memory read
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:

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

bash

# 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