CVE-2012-6531 in Zend Framework
Summary
by MITRE
(1) Zend_Dom, (2) Zend_Feed, and (3) Zend_Soap in Zend Framework 1.x before 1.11.13 and 1.12.x before 1.12.0 do not properly handle SimpleXMLElement classes, which allow remote attackers to read arbitrary files or create TCP connections via an external entity reference in a DOCTYPE element in an XML-RPC request, aka an XML external entity (XXE) injection attack, a different vulnerability than CVE-2012-3363.
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Analysis
by VulDB Data Team • 12/29/2021
The vulnerability identified as CVE-2012-6531 represents a critical XML external entity injection flaw affecting multiple components within the Zend Framework 1.x series. This vulnerability specifically impacts Zend_Dom, Zend_Feed, and Zend_Soap modules, which are widely used in web applications for document object model manipulation, feed parsing, and soap web service communication respectively. The flaw arises from inadequate handling of SimpleXMLElement classes during XML processing, creating a pathway for malicious actors to exploit the framework's XML parsing capabilities through carefully crafted requests. The vulnerability is particularly dangerous because it allows remote attackers to perform unauthorized file access and establish TCP connections, making it a significant threat to application security and data confidentiality.
The technical implementation of this vulnerability stems from the framework's insufficient validation of external entity references within XML documents. When processing XML-RPC requests containing DOCTYPE elements with external entity references, the affected Zend Framework components fail to properly sanitize or restrict these references. This occurs because SimpleXMLElement classes in PHP do not automatically disable external entity loading, leaving applications susceptible to XXE attacks. Attackers can construct malicious XML payloads that reference external entities pointing to local files or network resources, enabling them to read sensitive system files or establish connections to arbitrary hosts. The vulnerability is classified under CWE-611 as "Improper Restriction of XML External Entity Reference" and aligns with ATT&CK technique T1566.001 for "Phishing with Malicious Attachment" when used in initial compromise scenarios.
The operational impact of CVE-2012-6531 extends beyond simple data theft, as it provides attackers with a powerful vector for reconnaissance and lateral movement within affected systems. Successful exploitation can result in unauthorized access to sensitive files such as configuration files, database credentials, or application source code that might be stored in accessible locations. The ability to create TCP connections opens possibilities for establishing command and control channels or accessing internal network services that would otherwise be protected by firewalls. Organizations using affected versions of Zend Framework may experience data breaches, system compromise, and potential regulatory violations depending on the nature of the exposed information. The vulnerability affects a broad range of applications that rely on these framework components, making it particularly concerning for enterprises with extensive legacy systems.
Mitigation strategies for CVE-2012-6531 primarily focus on upgrading to patched versions of the Zend Framework, specifically versions 1.11.13 or 1.12.0 and later. Organizations should implement comprehensive patch management procedures to ensure all affected applications are updated promptly. Additional protective measures include configuring XML parsers to disable external entity resolution entirely by setting appropriate options in PHP's libxml configuration. Security teams should also implement network monitoring to detect unusual TCP connection patterns that might indicate exploitation attempts. Input validation and sanitization practices should be strengthened to prevent malformed XML from reaching vulnerable components. The vulnerability demonstrates the importance of secure coding practices and proper XML processing configurations, aligning with security standards such as OWASP Top 10 and NIST SP 800-53 requirements for input validation and secure configuration management. Organizations should conduct thorough security assessments to identify all applications using affected framework versions and prioritize remediation efforts based on risk exposure and business criticality.