CVE-2018-20664 in ADSelfService Plus
Summary
by MITRE
Zoho ManageEngine ADSelfService Plus 5.x before build 5701 has XXE via an uploaded product license.
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Analysis
by VulDB Data Team • 04/26/2020
The vulnerability identified as CVE-2018-20664 affects Zoho ManageEngine ADSelfService Plus version 5.x prior to build 5701, representing a critical XML External Entity processing flaw that enables remote attackers to execute arbitrary code or perform unauthorized data access. This vulnerability specifically manifests through the product license upload functionality, which fails to properly validate or sanitize XML input received from external sources. The flaw resides in the application's XML parser implementation that does not adequately restrict external entity references, allowing malicious actors to craft specially formatted license files that trigger unintended XML processing behaviors.
The technical exploitation of this vulnerability occurs when an attacker uploads a malicious XML license file that contains external entity declarations pointing to arbitrary resources or network locations. When the application processes this license file, the XML parser attempts to resolve these external entities, potentially leading to server-side request forgery attacks, local file inclusion scenarios, or remote code execution depending on the target system configuration and the specific XML processing implementation. The vulnerability falls under CWE-611, which specifically addresses Improper Restriction of XML External Entity Reference, a well-documented weakness in XML processing libraries that has been exploited in numerous security incidents across various platforms and applications.
From an operational impact perspective, this vulnerability presents significant risk to organizations using ManageEngine ADSelfService Plus as it allows attackers to potentially gain unauthorized access to sensitive system information, escalate privileges, or compromise the underlying infrastructure. The attack vector is particularly concerning because it leverages legitimate upload functionality that administrators would expect to be secure, making detection more challenging. Attackers could exploit this vulnerability to access internal network resources, retrieve sensitive configuration data, or establish persistent access points within the enterprise environment. The vulnerability aligns with ATT&CK technique T1059.007 for XML External Entity Processing and T1071.004 for Application Layer Protocol: DNS, as attackers might utilize these capabilities to establish command and control channels or exfiltrate data through external entity references.
Organizations should immediately apply the vendor-provided patch or upgrade to build 5701 or later versions that address this XXE vulnerability through proper input validation and XML parser hardening measures. Security teams should implement network monitoring to detect suspicious upload activities and XML processing patterns that may indicate exploitation attempts. Additional mitigations include restricting file upload permissions, implementing strict XML parsing configurations that disable external entity resolution, and conducting regular security assessments of web applications to identify similar vulnerabilities in other components. The remediation process should also include comprehensive testing to ensure that the patch does not introduce regressions in legitimate functionality while maintaining the security hardening measures that prevent future XXE vulnerabilities from emerging in the application's XML processing pathways.