CVE-2015-4147 in PHP
Summary
by MITRE
The SoapClient::__call method in ext/soap/soap.c in PHP before 5.4.39, 5.5.x before 5.5.23, and 5.6.x before 5.6.7 does not verify that __default_headers is an array, which allows remote attackers to execute arbitrary code by providing crafted serialized data with an unexpected data type, related to a "type confusion" issue.
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Analysis
by VulDB Data Team • 05/20/2022
The vulnerability identified as CVE-2015-4147 represents a critical type confusion flaw within PHP's SOAP extension that affects multiple versions of the PHP runtime environment. This issue resides in the SoapClient::__call method implementation within ext/soap/soap.c, where the software fails to properly validate the data type of the __default_headers parameter. The flaw enables remote attackers to manipulate serialized data structures in a manner that can lead to arbitrary code execution on the target system. The vulnerability is particularly dangerous because it operates at the core of PHP's web service communication capabilities, where SOAP clients are commonly used for interoperable application communication.
The technical nature of this vulnerability stems from improper input validation and type checking within the SOAP client implementation. When PHP processes SOAP requests, it expects __default_headers to be an array structure containing header information for the SOAP envelope. However, the vulnerable code does not verify that this parameter maintains the expected array type during deserialization of remote data. This type confusion allows attackers to inject malicious serialized objects where an array is expected, potentially causing the PHP interpreter to misinterpret memory structures and execute unintended operations. The issue manifests when crafted serialized data is passed through the SOAP client interface, leading to a scenario where the interpreter's type system becomes compromised.
The operational impact of CVE-2015-4147 extends beyond simple remote code execution to encompass significant system compromise potential. Attackers can leverage this vulnerability to execute arbitrary commands on vulnerable PHP servers, potentially gaining full control over web applications and underlying infrastructure. The attack vector typically involves sending specially crafted SOAP requests to PHP applications that utilize SoapClient functionality, making it particularly dangerous for web services, APIs, and enterprise applications that rely on SOAP communication protocols. This vulnerability directly relates to CWE-129, which addresses improper validation of array indices, and can be classified under ATT&CK technique T1059.007 for command and script injection. The widespread use of PHP in web applications means that exploitation of this vulnerability can affect numerous websites and services simultaneously.
Organizations affected by this vulnerability should implement immediate mitigations including updating to patched PHP versions, specifically PHP 5.4.39, 5.5.23, or 5.6.7 and later releases. Additionally, administrators should consider implementing network-level restrictions on SOAP traffic and monitoring for suspicious serialized data patterns in web application logs. The vulnerability highlights the importance of proper input validation and type checking in web application frameworks, particularly when handling serialized data from external sources. Security teams should also review their application code for any direct usage of SoapClient with untrusted input and implement proper sanitization measures to prevent exploitation of similar type confusion vulnerabilities in other components of the PHP ecosystem.