CVE-2015-8835 in PHP
Summary
by MITRE
The make_http_soap_request function in ext/soap/php_http.c in PHP before 5.4.44, 5.5.x before 5.5.28, and 5.6.x before 5.6.12 does not properly retrieve keys, which allows remote attackers to cause a denial of service (NULL pointer dereference, type confusion, and application crash) or possibly execute arbitrary code via crafted serialized data representing a numerically indexed _cookies array, related to the SoapClient::__call method in ext/soap/soap.c.
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Analysis
by VulDB Data Team • 08/19/2022
The vulnerability identified as CVE-2015-8835 represents a critical security flaw in PHP's SOAP extension that affects multiple versions of the PHP runtime environment. This issue resides within the make_http_soap_request function located in the ext/soap/php_http.c file, where improper handling of keys during data processing creates exploitable conditions that can lead to severe system compromise. The vulnerability specifically targets the SoapClient::__call method implementation in ext/soap/soap.c, creating a pathway for malicious actors to manipulate serialized data structures that represent numerically indexed _cookies arrays. The flaw manifests when PHP processes crafted serialized data that contains malformed cookie information, allowing attackers to manipulate internal data structures in ways that were not anticipated during the original development phase.
The technical exploitation of this vulnerability occurs through a combination of NULL pointer dereference conditions and type confusion errors that arise from the improper retrieval of keys during SOAP request processing. When PHP encounters serialized data containing a numerically indexed _cookies array, the make_http_soap_request function fails to properly validate or sanitize the key references, leading to memory corruption issues that can result in application crashes or more severe consequences. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions, while also demonstrating characteristics of CWE-129 which deals with insufficient validation of array indices and CWE-787 which involves out-of-bounds write operations. The vulnerability's potential for arbitrary code execution stems from the type confusion that occurs when PHP incorrectly interprets data types during the processing of maliciously crafted serialized arrays, allowing attackers to manipulate memory locations and potentially execute arbitrary commands with the privileges of the PHP process.
The operational impact of CVE-2015-8835 extends beyond simple denial of service scenarios to encompass potential complete system compromise when exploited successfully. Remote attackers can leverage this vulnerability to cause application crashes that result in service disruption, but more concerning is the possibility of achieving arbitrary code execution that could allow attackers to gain unauthorized access to affected systems. The vulnerability affects a wide range of PHP installations that utilize the SOAP extension, making it particularly dangerous in environments where web applications rely heavily on SOAP services for communication. Attackers can exploit this weakness by crafting malicious SOAP requests that contain specially formatted serialized cookie data, which when processed by vulnerable PHP versions can trigger the memory corruption conditions that lead to system compromise. This vulnerability is particularly concerning in web applications that process external SOAP requests or that use SoapClient functionality for service integration, as these applications become potential attack vectors for exploitation.
Organizations affected by this vulnerability should prioritize immediate patching of their PHP installations to address the security flaw in versions prior to 5.4.44, 5.5.28, and 5.6.12 respectively. The recommended mitigation strategy involves upgrading to patched PHP versions that contain the necessary code modifications to properly validate and sanitize key references during SOAP request processing. Additionally, administrators should implement network-level controls to restrict access to SOAP endpoints where possible and monitor for unusual patterns in SOAP request processing that might indicate exploitation attempts. The vulnerability's characteristics align with ATT&CK technique T1203 which involves exploiting weaknesses in software to gain unauthorized access, and T1499 which covers network disruption through service availability attacks. Security teams should also consider implementing input validation controls at the application level to prevent malformed serialized data from reaching the SOAP processing functions, creating additional layers of defense against exploitation attempts. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of vulnerable PHP installations within the organization's infrastructure.