CVE-2022-30522: Apache HTTP Server DoS Vulnerability

CVE-2022-30522 Overview

CVE-2022-30522 is a Denial of Service vulnerability affecting Apache HTTP Server version 2.4.53. When Apache HTTP Server is configured to perform transformations using the mod_sed module in contexts where the input data may be very large, the module can make excessively large memory allocations, ultimately triggering an abort and causing service disruption.

Critical Impact

This vulnerability enables remote attackers to cause a Denial of Service condition by sending specially crafted requests that trigger excessive memory allocation in mod_sed, potentially taking down affected web servers.

Affected Products

• Apache HTTP Server 2.4.53
• NetApp Clustered Data ONTAP
• Fedora 35 and Fedora 36

Discovery Timeline

• 2022-06-09 - CVE-2022-30522 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-30522

Vulnerability Analysis

This vulnerability is classified under CWE-789 (Memory Allocation with Excessive Size Value) and CWE-770 (Allocation of Resources Without Limits or Throttling). The mod_sed module in Apache HTTP Server is designed to perform stream editing operations on HTTP request and response bodies, similar to the Unix sed command. However, when processing input data of substantial size, the module fails to properly limit or validate memory allocation requests.

The vulnerability exists specifically in Apache HTTP Server version 2.4.53 when mod_sed is enabled and configured to process potentially large input streams. An attacker can exploit this by sending requests that cause the server to attempt memory allocations far exceeding available resources, leading to process termination.

Root Cause

The root cause stems from improper handling of memory allocation within the mod_sed module. When processing large input data, the module does not implement adequate checks or limits on the size of memory allocations it requests. This lack of resource constraints allows attackers to trigger allocation of excessive memory, which can exhaust server resources and cause the Apache process to abort. The issue relates to both CWE-789 (allocation with excessive size) and CWE-770 (unbounded resource allocation).

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can remotely exploit this vulnerability by:

1. Identifying Apache HTTP Server instances running version 2.4.53 with mod_sed enabled
2. Crafting HTTP requests containing large payloads designed to be processed by mod_sed
3. Sending these requests to trigger excessive memory allocation
4. Causing the server process to abort, resulting in denial of service

The vulnerability manifests when mod_sed processes input streams without proper size validation. Technical details about the specific memory allocation patterns can be found in the Apache HTTP Server Security Advisory and the Openwall OSS Security List discussion.

Detection Methods for CVE-2022-30522

Indicators of Compromise

• Unexpected Apache HTTP Server process crashes or restarts
• High memory consumption spikes preceding service termination
• Error logs showing memory allocation failures or abort signals
• Unusual patterns of large HTTP requests targeting endpoints processed by mod_sed

Detection Strategies

• Monitor Apache error logs for segmentation faults, abort signals, or out-of-memory conditions
• Implement alerting on Apache child process crashes or unexpected restarts
• Deploy web application firewall rules to detect abnormally large request bodies
• Analyze traffic patterns for requests targeting mod_sed-configured endpoints with oversized payloads

Monitoring Recommendations

• Configure system-level monitoring to track memory usage patterns for Apache processes
• Enable detailed Apache logging to capture request sizes and processing errors
• Implement automated alerts for service availability degradation
• Review and baseline normal memory allocation patterns for mod_sed operations

How to Mitigate CVE-2022-30522

Immediate Actions Required

• Upgrade Apache HTTP Server to a patched version newer than 2.4.53
• If immediate patching is not possible, consider disabling mod_sed if not required for operations
• Implement request size limits at the web server or load balancer level
• Deploy rate limiting to reduce the impact of potential exploitation attempts

Patch Information

Apache has released security updates addressing this vulnerability. System administrators should update to the latest stable version of Apache HTTP Server. Detailed patch information and updated packages are available through the Apache HTTP Server Security Advisory. Additional vendor-specific advisories are available from NetApp Security Advisory NTAP-20220624-0005 and Gentoo GLSA 202208-20. Fedora users can obtain patched packages via the distribution's update mechanism.

Workarounds

• Disable mod_sed module if it is not essential for server operations by commenting out or removing the LoadModule sed_module directive
• Implement input size restrictions using LimitRequestBody directive to cap maximum request body size
• Deploy a reverse proxy or WAF in front of Apache to filter and limit large request payloads
• Configure resource limits using system tools like ulimit to prevent runaway memory consumption from taking down the entire system

# Example Apache configuration to limit request body size
# Add to httpd.conf or relevant virtual host configuration
LimitRequestBody 10485760

# Disable mod_sed if not required (comment out the LoadModule line)
# LoadModule sed_module modules/mod_sed.so

# Set resource limits in systemd service file
# /etc/systemd/system/httpd.service.d/limits.conf
# [Service]
# MemoryLimit=2G