CVE-2022-28615: Apache HTTP Server DOS Vulnerability

CVE-2022-28615 Overview

CVE-2022-28615 is an Out-of-Bounds Read vulnerability affecting Apache HTTP Server versions 2.4.53 and earlier. The vulnerability exists in the ap_strcmp_match() function, which may read beyond bounds when provided with an extremely large input buffer. This can result in a server crash (denial of service) or potential information disclosure.

While no code distributed with the core Apache HTTP Server can be coerced into triggering this vulnerability, third-party modules or Lua scripts that utilize the ap_strcmp_match() function may hypothetically be affected. Organizations running custom modules or Lua-based configurations should assess their exposure.

Critical Impact

This vulnerability can lead to server crashes causing denial of service, and may expose sensitive memory contents through information disclosure when exploited via third-party modules or Lua scripts using the vulnerable ap_strcmp_match() function.

Affected Products

• Apache HTTP Server versions up to and including 2.4.53
• Fedora 35 and Fedora 36
• NetApp Clustered Data ONTAP

Discovery Timeline

• 2022-06-09 - CVE-2022-28615 published to NVD
• 2025-12-18 - Last updated in NVD database

Technical Details for CVE-2022-28615

Vulnerability Analysis

This vulnerability stems from an Integer Overflow issue (CWE-190) in the ap_strcmp_match() function within Apache HTTP Server. When this function receives an extremely large input buffer, it fails to properly validate buffer boundaries before performing comparison operations. This boundary validation failure allows read operations to access memory beyond the allocated buffer space.

The function is used for wildcard pattern matching operations, which are common in URL rewriting, access control, and request handling. When third-party modules or Lua scripts pass oversized inputs to this function without proper validation, the resulting out-of-bounds read can expose adjacent memory contents or trigger a segmentation fault.

The network-accessible nature of this vulnerability combined with the lack of required authentication and low attack complexity makes it particularly concerning for internet-facing Apache deployments. However, the actual exploitability depends on whether the server deployment includes vulnerable third-party components that can be manipulated to pass malicious input to ap_strcmp_match().

Root Cause

The root cause is an Integer Overflow (CWE-190) in the ap_strcmp_match() function. When processing extremely large input buffers, the function fails to properly handle integer boundaries during buffer length calculations. This leads to incorrect boundary checks, allowing subsequent read operations to access memory locations beyond the intended buffer limits.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker would need to identify a third-party module or Lua script that passes user-controllable input to the ap_strcmp_match() function. By crafting requests with extremely large input values, the attacker can trigger the out-of-bounds read condition.

The attack flow involves:

1. Identifying a target Apache server with vulnerable third-party modules or Lua scripts
2. Crafting HTTP requests with extremely large input parameters that reach ap_strcmp_match()
3. Triggering the integer overflow condition to cause out-of-bounds memory access
4. Observing server behavior for crash conditions or extracting leaked information from error responses

Since no verified exploit code is publicly available, the specific exploitation technique would vary based on the third-party component being targeted. For detailed technical information, refer to the Openwall Security Discussion and the Apache HTTP Server Security Vulnerabilities page.

Detection Methods for CVE-2022-28615

Indicators of Compromise

• Unexpected Apache HTTP Server crashes or segmentation faults in error logs
• HTTP requests containing abnormally large parameter values or headers
• Memory access violations in Apache child processes
• Core dump files generated by Apache processes indicating memory corruption

Detection Strategies

• Monitor Apache error logs for segmentation faults and unexpected child process terminations
• Implement web application firewall (WAF) rules to detect and block requests with oversized input parameters
• Use intrusion detection systems (IDS) to identify patterns of requests targeting known vulnerable modules
• Audit third-party Apache modules and Lua scripts for usage of ap_strcmp_match() function

Monitoring Recommendations

• Configure centralized logging to aggregate Apache error logs for anomaly detection
• Set up alerts for Apache process crashes and restart events
• Monitor memory usage patterns of Apache processes for signs of memory leaks or corruption
• Track request sizes and flag anomalously large HTTP requests for review

How to Mitigate CVE-2022-28615

Immediate Actions Required

• Upgrade Apache HTTP Server to version 2.4.54 or later, which contains the security fix
• Audit all third-party modules and Lua scripts for usage of ap_strcmp_match() function
• Implement input size validation at the web application firewall level
• Review and update all dependent systems including Fedora and NetApp Clustered Data ONTAP installations

Patch Information

Apache has released a security patch addressing this vulnerability in Apache HTTP Server version 2.4.54. Organizations should upgrade to this version or later to fully remediate the vulnerability. Detailed patch information is available in the Apache HTTP Server Security Vulnerabilities advisory.

Additional vendor-specific patches are available:

• Fedora Package Announcements
• NetApp Security Advisory
• Gentoo GLSA 202208-20

Workarounds

• Configure request size limits in Apache to restrict maximum input buffer sizes
• Disable or remove unnecessary third-party modules, particularly those using pattern matching functions
• Implement reverse proxy with input validation to filter malformed requests before they reach Apache
• Use mod_security or similar WAF modules to enforce strict input validation rules

# Example Apache configuration to limit request body size
# Add to httpd.conf or appropriate virtual host configuration
LimitRequestBody 1048576
LimitRequestFields 50
LimitRequestFieldSize 8190
LimitRequestLine 8190