✅ Report Title:
PHP Vulnerability Analysis: CVE-2026-109618, CVE-2026-109619

✅ Executive Summary

📌 What is PHP?

• PHP is a server-side scripting language widely used for web application development. It processes HTTP requests, generates dynamic web content, and supports database interactions. PHP is commonly used in e-commerce platforms, blogs, and content management systems such as WordPress.

📌 Vulnerability Overview

• On October 20, 2026, the Remote Code Execution vulnerabilities in PHP, CVE-2026-109618 and CVE-2026-109619, were disclosed.
• These vulnerabilities affect the product versions listed below.
  • PHP 8.5 series < 8.5.12
  • PHP 8.4 series < 8.4.27
  • PHP 8.3 series < 8.3.36
  • PHP 8.2 series < 8.2.35
  • PHP 8.1 / 8.0 / 7.4 series (all versions affected)
  • PHP 5.4 ~ 7.3 series (all versions affected, impact varies by attack vector)
• On October 20, 2026, both vulnerabilities were rated CVSS v4.0: 9.2 (Critical). Reviewing the mitigation measures and responding promptly is recommended.

📌 Root Cause of the Vulnerabilities

• These are remote code execution (RCE) vulnerabilities that occur when PHP abnormally terminates request processing due to memory exhaustion or a fatal error, leaving request memory either uninitialized or already freed.
• CVE-2026-109618
  • When memory allocation fails, PHP abnormally terminates the execution flow via zend_bailout(), which can leave some data structures incompletely initialized.
  • An attacker can repeatedly trigger this condition by using multipart requests to drive memory usage up to the memory_limit.
  • During request termination, PHP traverses data structures that were not fully initialized in order to free memory. Treating an invalid entry as valid data during this process can cause memory corruption.
  • In Apache mod_php environments, the termination procedure runs even when request initialization fails, meaning the vulnerability can be triggered before any application code executes.
• CVE-2026-109619
  • PHP can store, in the global state used for sessions, error handling, objects, and extension modules, pointers that reference the per-request heap memory.
  • If a request is interrupted by an out-of-memory (OOM) condition or a fatal error, the pointer-clearing routine is skipped, leaving invalid pointers in the global state even after the request memory has been freed.
  • When the same PHP worker later processes a new HTTP request, referencing that global state before initialization completes can trigger a Use-After-Free.
  • A representative case occurs during Session Upload Progress processing, where PS(id) or PS(http_session_vars) is referenced while pointing to freed memory, which can lead to memory corruption or information disclosure.
  • During error backtrace processing, EG(last_fatal_error_backtrace) can be referenced while pointing to freed memory, leading to memory corruption. This applies when the fatal_error_backtraces setting is enabled in PHP 8.5.

✅ Threat Detection Recommendations and Mitigation Measures:

• Update threat detection rules, maintain continuous monitoring, and apply the security updates provided by the vendor.
  • PHP 8.5 series ≥ 8.5.12
  • PHP 8.4 series ≥ 8.4.27
  • PHP 8.3 series ≥ 8.3.36
  • PHP 8.2 series ≥ 8.2.35
• PHP 8.1 / 8.0 / 7.4 do not have official patch releases; a manual build using the minimal source backport branch provided by the PHP security team is required before applying a fix.
• PHP 5.4 through 7.3 and earlier EOL legacy versions have no official patch available. Upgrading to the latest PHP version is recommended.
• If immediate patching is not possible, it is recommended to apply the following mitigation measures:
  • Disable the PHP Session Upload Progress feature: set session.upload_progress.enabled = 0
  • Remove the PHP script memory limit: set memory_limit = -1
  • This is a temporary workaround to reduce the likelihood of OOM conditions and is not a fundamental mitigation for the vulnerability itself.
  • Raising or removing the memory usage limit carries a risk of memory exhaustion, so an appropriate limit should be applied with the operating environment in mind.
• Until the vulnerable service is patched, it is recommended to suspend external exposure of internet-facing PHP-based services and restrict access to authorized users and networks only, via internal networks or VPNs.