CVE-2015-1646 in XML Core Services
Summary
by MITRE
Microsoft XML Core Services (aka MSXML) 3.0 allows remote attackers to bypass the Same Origin Policy and obtain sensitive information via a crafted DTD, aka "MSXML3 Same Origin Policy SFB Vulnerability."
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Analysis
by VulDB Data Team • 11/30/2024
The vulnerability identified as CVE-2015-1646 affects Microsoft XML Core Services version 3.0, specifically targeting the Same Origin Policy implementation within the MSXML component. This flaw represents a critical security weakness that undermines fundamental web security mechanisms designed to prevent unauthorized cross-origin resource access. The vulnerability stems from an insufficient validation of external entity declarations within Document Type Definitions, allowing malicious actors to craft specially formatted DTDs that can circumvent standard browser security restrictions.
The technical exploitation of this vulnerability occurs through the manipulation of XML parsing behavior in MSXML 3.0, where the system fails to properly enforce same origin policy restrictions when processing external entities. Attackers can construct malicious DTDs that reference external resources from different origins, effectively bypassing the security boundaries that normally prevent web applications from accessing content from other domains. This weakness falls under CWE-200, which addresses information exposure through improper access control, and specifically relates to CWE-94, which covers improper control of generation of code, as the vulnerability enables unauthorized code execution through XML manipulation.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to perform cross-origin data exfiltration and potentially execute malicious payloads. When exploited, the vulnerability allows remote attackers to access sensitive information that should normally be restricted by browser security policies, including data from other domains, cookies, and potentially authentication tokens. This represents a significant threat to web applications that rely on MSXML for XML processing, particularly those handling sensitive user data or implementing cross-domain communication patterns.
The attack vector typically involves delivering malicious XML content to a victim's browser through various means such as web pages, email attachments, or compromised web services. The vulnerability affects systems running MSXML 3.0 and can be exploited in environments where XML processing is performed without proper input validation. Organizations implementing security controls should consider this vulnerability in their risk assessment frameworks, particularly when evaluating their web application security posture and XML processing capabilities. The flaw demonstrates the importance of proper input validation and the potential consequences of inadequate security controls in core system components.
Mitigation strategies should include immediate patching of affected MSXML 3.0 installations, implementation of proper XML input validation, and deployment of web application firewalls that can detect and block malicious XML content. Security teams should also implement monitoring for unusual XML processing patterns and consider restricting external entity access in XML parsers. The vulnerability highlights the necessity of maintaining up-to-date security patches and the importance of following security best practices such as those recommended in the OWASP Top Ten and NIST cybersecurity guidelines. Organizations should conduct thorough vulnerability assessments to identify all systems running affected MSXML versions and implement comprehensive security monitoring to detect potential exploitation attempts.