CVE-2014-4670 in PHP
Summary
by MITRE
Use-after-free vulnerability in ext/spl/spl_dllist.c in the SPL component in PHP through 5.5.14 allows context-dependent attackers to cause a denial of service or possibly have unspecified other impact via crafted iterator usage within applications in certain web-hosting environments.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 02/08/2022
The CVE-2014-4670 vulnerability represents a critical use-after-free flaw within PHP's Standard PHP Library component, specifically in the spl_dllist.c file that manages doubly linked list data structures. This vulnerability exists in PHP versions through 5.5.14 and demonstrates how improper memory management can create significant security risks in web applications. The flaw manifests when applications utilize SPL iterators in web hosting environments where PHP is compiled with specific configurations that enable certain memory allocation patterns. The vulnerability classifies as a memory corruption issue that can potentially be exploited to cause system instability or more severe consequences depending on the execution context.
The technical implementation of this vulnerability stems from improper handling of memory references within the SPL doubly linked list implementation. When PHP applications create or manipulate iterator objects that traverse doubly linked lists, the underlying code fails to properly validate memory references before accessing freed memory locations. This occurs during iterator operations where the system may attempt to dereference pointers that have already been deallocated, leading to unpredictable behavior. The vulnerability specifically affects scenarios where iterator objects are used in contexts where memory is freed but references remain active, creating a window where attackers can manipulate the execution flow through carefully crafted input sequences.
The operational impact of CVE-2014-4670 extends beyond simple denial of service to potentially enable more sophisticated attack vectors depending on the hosting environment and application configuration. In web hosting contexts where PHP applications are executed with elevated privileges or where memory corruption can be leveraged for code execution, this vulnerability could theoretically allow attackers to execute arbitrary code or escalate privileges. The context-dependent nature of the exploit means that successful exploitation requires specific environmental conditions including the PHP compilation flags, memory management settings, and application code patterns that trigger the problematic code path. Attackers typically need to craft input that specifically triggers the iterator usage pattern within SPL components to activate the vulnerability.
Mitigation strategies for this vulnerability primarily focus on immediate PHP version upgrades to patched releases, as the flaw was addressed in subsequent PHP versions through proper memory management fixes. System administrators should prioritize updating PHP installations to versions 5.5.15 or later, where the memory handling in spl_dllist.c has been corrected to prevent use-after-free conditions. Additionally, implementing proper input validation and sanitization measures can reduce the attack surface by limiting the types of iterator operations that applications perform. Organizations should also consider applying runtime security controls such as PHP hardening configurations, disabling unnecessary SPL functions, and implementing application firewalls that can detect and block suspicious iterator usage patterns. The vulnerability demonstrates the importance of proper memory management practices and aligns with CWE-416 which addresses use-after-free conditions, while potentially mapping to ATT&CK techniques involving privilege escalation and code injection through memory corruption vulnerabilities.