CVE-2017-14699 in ASUS DSL-AC51
Summary
by MITRE
Multiple XML external entity (XXE) vulnerabilities in the AiCloud feature on ASUS DSL-AC51, DSL-AC52U, DSL-AC55U, DSL-N55U C1, DSL-N55U D1, DSL-AC56U, DSL-N10_C1, DSL-N12U C1, DSL-N12E C1, DSL-N14U, DSL-N14U-B1, DSL-N16, DSL-N16U, DSL-N17U, DSL-N66U, and DSL-AC750 routers allow remote authenticated users to read arbitrary files via a crafted DTD in (1) an UPDATEACCOUNT or (2) a PROPFIND request.
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Analysis
by VulDB Data Team • 12/31/2019
The vulnerability identified as CVE-2017-14699 represents a critical XML external entity (XXE) flaw discovered within the AiCloud feature of multiple ASUS router models including the DSL-AC51, DSL-AC52U, DSL-AC55U, and numerous other variants. This vulnerability resides in the router's web interface handling of XML data processing, specifically when processing UPDATEACCOUNT and PROPFIND requests. The flaw allows authenticated remote attackers to exploit XML parsing mechanisms by injecting malicious external entity references through crafted Document Type Definition (DTD) files. The vulnerability stems from insufficient input validation and improper handling of external entity declarations within the XML processing pipeline of the affected router firmware versions.
The technical implementation of this vulnerability follows the standard XXE attack pattern where an attacker can manipulate XML parsers to resolve external references and access local system resources. When the router processes XML data containing malicious DTD declarations, the XML parser attempts to resolve external entities, potentially allowing access to sensitive files on the router's filesystem. This includes reading configuration files, user credentials, system logs, and other potentially sensitive data that should remain protected within the device's internal storage. The authentication requirement means that an attacker must first obtain valid credentials to exploit this vulnerability, but once authenticated, the impact extends to unauthorized file access and potential information disclosure.
The operational impact of this vulnerability is significant for network security and device management. An authenticated attacker with access to router administration can leverage this XXE vulnerability to extract confidential information from the device's local storage, potentially compromising user credentials, network configurations, and other sensitive operational data. This represents a privilege escalation risk when combined with the authentication requirement, as it allows attackers to access more information than they should be authorized to view. The vulnerability affects multiple router models across different generations, indicating a widespread issue within ASUS firmware implementations and potentially exposing numerous devices to similar risks.
Mitigation strategies for CVE-2017-14699 should focus on firmware updates from ASUS to address the specific XXE parsing vulnerabilities in the AiCloud feature. Network administrators should implement strict access controls and authentication measures to limit who can access router management interfaces, as the vulnerability requires authentication to exploit. Additionally, implementing network segmentation and monitoring for unusual XML processing patterns can help detect potential exploitation attempts. The vulnerability aligns with CWE-611 (Improper Restriction of XML External Entity Reference) and relates to ATT&CK technique T1213.002 (External Remote Services) as it involves exploitation of remote management interfaces. Organizations should also consider disabling unnecessary web services and features like AiCloud when not actively required, reducing the attack surface available to potential attackers. Regular security assessments and vulnerability scanning should be conducted to identify similar XXE vulnerabilities in other network devices and applications.