CVE-2015-4603 in PHP
Summary
by MITRE
The exception::getTraceAsString function in Zend/zend_exceptions.c in PHP before 5.4.40, 5.5.x before 5.5.24, and 5.6.x before 5.6.8 allows remote attackers to execute arbitrary code via an unexpected data type, related to a "type confusion" issue.
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Analysis
by VulDB Data Team • 05/22/2022
The vulnerability identified as CVE-2015-4603 represents a critical type confusion flaw within PHP's exception handling mechanism that affects multiple versions of the PHP runtime environment. This issue resides in the Zend/zend_exceptions.c file where the exception::getTraceAsString function fails to properly validate data types during exception processing, creating a pathway for remote code execution attacks. The vulnerability manifests when attackers can manipulate input data to trigger unexpected type behavior within the PHP engine's internal exception handling routines.
The technical root cause of this vulnerability stems from improper type validation within the PHP engine's exception trace processing logic. When the getTraceAsString function processes exception data, it does not adequately check the data types of incoming parameters, allowing attackers to inject malformed data that causes the engine to interpret memory locations as executable code. This type confusion vulnerability enables attackers to manipulate the PHP interpreter's internal state, potentially leading to arbitrary code execution on the affected system. The flaw specifically affects PHP versions before 5.4.40, 5.5.x before 5.5.24, and 5.6.x before 5.6.8, making it a widespread issue across multiple PHP release lines.
From an operational perspective, this vulnerability poses significant risks to web applications running on affected PHP versions, as it can be exploited remotely without authentication. Attackers can leverage this flaw by crafting malicious input that triggers exception handling code paths, potentially leading to complete system compromise. The vulnerability's impact extends beyond simple code execution to include potential privilege escalation and data exfiltration scenarios, making it particularly dangerous in web server environments where PHP applications process untrusted user input. Organizations running vulnerable PHP versions face substantial risk of unauthorized access, data breaches, and system compromise.
Security professionals should prioritize immediate patching of affected PHP installations to mitigate this vulnerability. The recommended mitigation involves upgrading to PHP versions 5.4.40, 5.5.24, or 5.6.8 respectively, which contain fixes for the type confusion issue in the exception handling code. Additionally, implementing web application firewalls and input validation measures can provide temporary protection while patches are deployed. This vulnerability aligns with CWE-129 and CWE-787 categories related to improper input validation and out-of-bounds writes, and it maps to ATT&CK technique T1059.007 for command and scripting interpreter usage. Organizations should also consider implementing runtime monitoring to detect potential exploitation attempts and maintain comprehensive incident response procedures to address any successful attacks.