CVE-2024-11235: PHP Use-After-Free RCE Vulnerability

CVE-2024-11235 Overview

CVE-2024-11235 is a critical use-after-free vulnerability affecting PHP versions 8.3.* before 8.3.19 and 8.4.* before 8.4.5. The vulnerability exists in a code sequence involving the __set handler or the null coalescing assignment operator (??=) combined with exceptions. When triggered, this flaw can lead to memory corruption that may be exploited for remote code execution if an attacker can control the memory layout through specially crafted inputs.

Critical Impact

This use-after-free vulnerability can be exploited remotely to achieve code execution on systems running vulnerable PHP versions, potentially allowing complete system compromise of web servers and applications.

Affected Products

• PHP versions 8.3.* before 8.3.19
• PHP versions 8.4.* before 8.4.5

Discovery Timeline

• 2025-04-04 - CVE CVE-2024-11235 published to NVD
• 2025-04-30 - Last updated in NVD database

Technical Details for CVE-2024-11235

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free), a memory corruption vulnerability that occurs when a program continues to use a pointer after the memory it references has been freed. In the context of PHP, this vulnerability manifests in specific code paths involving PHP's magic method __set handler and the null coalescing assignment operator (??=) when exceptions are thrown during these operations.

The attack requires network access and involves complex attack prerequisites where an attacker must be able to supply specially crafted inputs to a PHP script that exercises the vulnerable code path. If the attacker can successfully control the memory layout, they may be able to manipulate freed memory to achieve arbitrary code execution within the PHP interpreter context.

Root Cause

The root cause lies in improper memory management within PHP's internal handling of the __set magic method and the ??= operator when exceptions occur. During exception handling in these code sequences, PHP fails to properly track memory references, leading to a condition where a memory region is freed but a dangling pointer to that memory remains accessible. Subsequent operations using this dangling pointer can read or write to memory that has been reallocated for other purposes, creating an exploitable condition.

Attack Vector

The attack vector is network-based, allowing remote exploitation without requiring authentication or user interaction. An attacker can target vulnerable PHP applications by:

1. Identifying a PHP application using affected versions that processes user-controlled input
2. Crafting malicious input designed to trigger the vulnerable __set or ??= code path
3. Manipulating memory layout through carefully timed inputs to control the freed memory region
4. Executing arbitrary code within the context of the PHP process

The vulnerability is exploitable through any network-accessible PHP application that processes attacker-controlled data and exercises the vulnerable code paths. Web applications accepting user input via forms, APIs, or file uploads are potential targets.

Detection Methods for CVE-2024-11235

Indicators of Compromise

• Unexpected PHP process crashes or segmentation faults in web server logs
• Anomalous memory consumption patterns in PHP-FPM or Apache mod_php processes
• Unusual child process spawning from PHP interpreter processes
• Web application log entries showing malformed or exceptionally long input parameters

Detection Strategies

• Monitor PHP error logs for segmentation faults, memory corruption errors, or unexpected exception chains involving __set handlers
• Implement web application firewall (WAF) rules to detect and block suspicious payloads targeting PHP applications
• Deploy runtime application self-protection (RASP) solutions capable of detecting memory corruption attempts
• Use SentinelOne's Singularity platform to detect anomalous behavior from PHP processes including unexpected system calls or memory access patterns

Monitoring Recommendations

• Enable verbose PHP error logging and centralize logs for security analysis
• Configure process monitoring to alert on PHP processes exhibiting abnormal memory behavior
• Implement network traffic analysis to identify exploitation attempts targeting PHP endpoints
• Deploy endpoint detection and response (EDR) solutions like SentinelOne to monitor for post-exploitation activity

How to Mitigate CVE-2024-11235

Immediate Actions Required

• Upgrade PHP to version 8.3.19 or later for the 8.3 branch
• Upgrade PHP to version 8.4.5 or later for the 8.4 branch
• Review and restrict network access to PHP applications where immediate patching is not possible
• Implement web application firewall rules to add an additional layer of protection

Patch Information

PHP has released security updates addressing this vulnerability. Organizations should upgrade to PHP 8.3.19 or 8.4.5 or later versions as appropriate for their deployment. The official security advisory is available at the PHP GitHub Security Advisory which provides detailed information about the fix.

Workarounds

• Isolate PHP applications using containerization or sandboxing technologies to limit the impact of potential exploitation
• Implement strict input validation at the application layer to reduce attack surface
• Consider disabling or restricting the use of __set magic methods in critical applications until patching is complete
• Deploy SentinelOne Singularity for real-time detection and automated response to exploitation attempts

# Check current PHP version
php -v

# Update PHP on Debian/Ubuntu systems
sudo apt update && sudo apt install php8.3

# Update PHP on RHEL/CentOS systems
sudo dnf update php

# Verify patched version is installed
php -v | grep -E "8\.(3\.19|4\.5)"