CVE-2017-3839 in Secure Access Control System
Summary
by MITRE
An XML External Entity vulnerability in the web-based user interface of the Cisco Secure Access Control System (ACS) could allow an unauthenticated, remote attacker to have read access to part of the information stored in the affected system. More Information: CSCvc04845. Known Affected Releases: 5.8(2.5).
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Analysis
by VulDB Data Team • 12/25/2024
The Cisco Secure Access Control System ACS represents a critical component in enterprise network security infrastructure, providing centralized authentication and authorization services for network access control. This vulnerability resides within the web-based user interface of the system, creating a significant attack surface that could be exploited by malicious actors without requiring authentication credentials. The affected version 5.8(2.5) demonstrates how even well-established security platforms can contain fundamental flaws that compromise their integrity. The vulnerability specifically manifests as an XML External Entity processing issue that allows remote attackers to manipulate the system's data handling mechanisms through crafted XML input.
The technical flaw exploits the improper handling of XML entities within the web interface components of the Cisco ACS platform. When the system processes XML data containing external entity references, it fails to properly validate or sanitize these inputs, enabling attackers to construct malicious XML payloads that can access internal system resources. This vulnerability operates at the application layer and leverages the inherent capabilities of XML parsers to resolve external references, which in this case becomes a vector for unauthorized information disclosure. The flaw aligns with CWE-611, which specifically addresses improper restriction of XML external entity reference, a category that has been consistently identified as a critical security risk in enterprise applications. Attackers can construct XML documents that reference external resources and potentially access sensitive data stored within the system's internal file structures.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates opportunities for further exploitation and reconnaissance activities. An unauthenticated attacker could potentially extract configuration data, user credentials, or other sensitive information that would normally be protected within the system's secure boundaries. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter, eliminating the need for physical access or internal network presence. This characteristic places the vulnerability in the ATT&CK framework under the T1046 category for Network Service Scanning and T1005 for Data from Local System, as attackers can leverage this vulnerability to gather intelligence about the target environment. The affected system's role as a central authentication point makes this vulnerability particularly dangerous, as it could potentially provide attackers with access to authentication databases or configuration information that could be used for additional attacks.
Organizations should implement immediate mitigations including applying the vendor-provided security patches and updates to address the XML external entity processing flaw. Network segmentation and access controls should be enhanced to limit exposure of the affected web interface to trusted networks only. Regular security assessments and input validation testing should be conducted to identify similar vulnerabilities in other applications and systems. The vulnerability highlights the importance of proper XML parsing practices and input sanitization in web applications, particularly those handling sensitive enterprise data. Additionally, implementing web application firewalls and content filtering mechanisms can provide additional layers of protection against similar attacks. Organizations should also consider conducting thorough vulnerability assessments of their entire network infrastructure to identify other potential XML external entity vulnerabilities that may exist in legacy systems or third-party applications.