CVE-2015-8880 in PHP
Summary
by MITRE
Double free vulnerability in the format printer in PHP 7.x before 7.0.1 allows remote attackers to have an unspecified impact by triggering an error.
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Analysis
by VulDB Data Team • 12/09/2018
The CVE-2015-8880 vulnerability represents a critical double free condition within PHP's format printer functionality affecting versions prior to 7.0.1. This flaw exists in the handling of error conditions within PHP's internal formatting mechanisms, specifically when processing certain error scenarios that involve memory allocation and deallocation patterns. The vulnerability manifests when the format printer encounters specific error conditions that trigger improper memory management sequences, leading to the same memory block being freed twice. This type of vulnerability falls under the broader category of memory corruption issues that can lead to arbitrary code execution or system instability. The double free condition occurs in PHP's internal error handling routines where the system attempts to release memory that has already been deallocated, creating a potential exploitation vector for remote attackers. The vulnerability is particularly concerning because it operates within the core PHP processing engine, making it accessible through standard web application interactions that utilize PHP's formatting functions.
The technical implementation of this vulnerability stems from improper memory management within PHP 7.x's format printer component, which handles the formatting of various data types for output purposes. When an error condition occurs during the formatting process, the internal memory deallocation routines fail to properly track memory state, resulting in the same memory block being freed multiple times. This type of memory corruption vulnerability is classified as CWE-415, which specifically addresses double free conditions in memory management. The flaw exists in the interaction between PHP's error reporting system and its memory allocation mechanisms, where error handling code paths do not properly validate memory state before attempting deallocation operations. The vulnerability can be triggered through crafted input that causes PHP to enter error conditions within the format printer, potentially allowing attackers to manipulate memory layout or execute arbitrary code.
The operational impact of CVE-2015-8880 extends beyond simple system instability, as remote attackers can leverage this vulnerability to execute arbitrary code on affected systems. The unspecified impact mentioned in the original description reflects the potential for various malicious outcomes including complete system compromise, data exfiltration, or service disruption. When exploited successfully, the double free condition can lead to heap corruption that allows attackers to manipulate program execution flow, potentially enabling code injection attacks or privilege escalation. The vulnerability affects web applications running on PHP 7.x versions before 7.0.1, making it particularly dangerous for web servers and application environments where PHP is the primary scripting language. Attackers can trigger this vulnerability through malicious input that causes PHP to process formatting operations in error conditions, effectively creating a remote code execution vector. The attack surface is broad as any web application utilizing PHP's formatting functions could be affected, particularly those that process user input through format printing operations.
Mitigation strategies for CVE-2015-8880 primarily focus on immediate version updates and proper input validation practices. The most effective remediation involves upgrading PHP installations to version 7.0.1 or later, where the memory management issues have been addressed through improved error handling and memory tracking mechanisms. Organizations should implement comprehensive patch management procedures to ensure all PHP installations are updated promptly. Additionally, implementing strict input validation and sanitization practices can help reduce the attack surface by preventing malicious input from reaching the vulnerable format printer functions. Network-level protections such as web application firewalls and intrusion detection systems can provide additional layers of defense by monitoring for suspicious input patterns that may trigger the vulnerability. The vulnerability's classification under ATT&CK framework as a memory corruption technique emphasizes the importance of defensive measures including heap hardening, address space layout randomization, and runtime protection mechanisms. Regular security assessments and code reviews focusing on memory management practices within PHP applications can help identify and remediate similar vulnerabilities in custom code implementations.