CVE-2024-11236: PHP ldap_escape() Buffer Overflow Flaw

CVE-2024-11236 Overview

CVE-2024-11236 is a critical integer overflow vulnerability affecting PHP's ldap_escape() function on 32-bit systems. When processing uncontrolled long string inputs, the function fails to properly validate input length, causing an integer overflow that results in an out-of-bounds write condition. This memory corruption vulnerability can potentially allow attackers to execute arbitrary code or crash the application.

Critical Impact

This vulnerability enables remote attackers to trigger memory corruption through crafted input to the ldap_escape() function on 32-bit PHP installations, potentially leading to arbitrary code execution or denial of service.

Affected Products

• PHP versions 8.1.* before 8.1.31
• PHP versions 8.2.* before 8.2.26
• PHP versions 8.3.* before 8.3.14

Discovery Timeline

• 2024-11-24 - CVE-2024-11236 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2024-11236

Vulnerability Analysis

The vulnerability exists in PHP's ldap_escape() function, which is designed to escape special characters in strings used in LDAP queries. On 32-bit systems, the function performs arithmetic operations on the input string length without adequate overflow protection. When an attacker supplies an exceptionally long string, the length calculation overflows, causing the function to allocate an insufficient buffer. Subsequent write operations then exceed the allocated memory boundaries, corrupting adjacent memory regions.

This flaw is classified under CWE-190 (Integer Overflow or Wraparound) and CWE-787 (Out-of-bounds Write). The vulnerability is particularly dangerous because it affects a function commonly used in authentication workflows where user-supplied input may be processed.

Root Cause

The root cause stems from improper integer handling in the ldap_escape() function's buffer size calculation logic. On 32-bit architectures, the maximum integer value is 2,147,483,647 (2^31-1). When calculating the required buffer size for escaped output, the function multiplies the input length by a factor to account for escaped characters. With sufficiently large input strings, this multiplication can exceed the maximum integer value, wrapping around to a small or negative number. The subsequent memory allocation uses this incorrect size, creating an undersized buffer that is then overwritten during the escape operation.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by sending HTTP requests containing extremely long strings to a PHP application that processes LDAP-related input through the ldap_escape() function on a 32-bit system.

The vulnerability manifests when the ldap_escape() function processes oversized string inputs, causing integer overflow during buffer size calculations. This results in undersized memory allocation followed by out-of-bounds memory writes. For detailed technical analysis and proof-of-concept information, refer to the GitHub Security Advisory.

Detection Methods for CVE-2024-11236

Indicators of Compromise

• Abnormally large HTTP request payloads targeting PHP applications with LDAP functionality
• PHP process crashes or segmentation faults on 32-bit systems
• Memory corruption errors in PHP error logs associated with LDAP operations
• Unusual memory allocation patterns in web server processes

Detection Strategies

• Monitor for HTTP requests with unusually large string parameters directed at LDAP-related endpoints
• Implement application-level logging to track ldap_escape() function calls with input size metrics
• Deploy web application firewalls (WAF) with rules to detect and block oversized input strings
• Use memory analysis tools to detect out-of-bounds write attempts in PHP processes

Monitoring Recommendations

• Enable PHP error logging and monitor for memory-related errors and crashes
• Implement request size limits at the web server and application level
• Monitor system logs for segmentation faults in PHP processes
• Track PHP process memory usage for anomalous patterns indicating exploitation attempts

How to Mitigate CVE-2024-11236

Immediate Actions Required

• Upgrade PHP 8.1.x installations to version 8.1.31 or later immediately
• Upgrade PHP 8.2.x installations to version 8.2.26 or later immediately
• Upgrade PHP 8.3.x installations to version 8.3.14 or later immediately
• Prioritize patching 32-bit systems as they are specifically vulnerable to this integer overflow

Patch Information

PHP has released security patches addressing this vulnerability in the following versions: 8.1.31, 8.2.26, and 8.3.14. Organizations should update to these versions or later to remediate the vulnerability. Additional vendor-specific advisories are available from Debian LTS and NetApp.

Workarounds

• Implement strict input length validation before calling ldap_escape() to reject oversized strings
• Deploy web application firewall rules to limit maximum request body and parameter sizes
• Consider migrating 32-bit PHP installations to 64-bit systems where this integer overflow cannot occur
• Isolate PHP processes handling LDAP operations using containerization or sandboxing

# Example: Configure Apache to limit request body size
# Add to httpd.conf or .htaccess
LimitRequestBody 1048576

# Example: Configure nginx to limit client body size
# Add to nginx.conf server block
client_max_body_size 1m;