CVE-2016-7458 in vSphere Client
Summary
by MITRE
VMware vSphere Client 5.5 before U3e and 6.0 before U2a allows remote vCenter Server and ESXi instances to read arbitrary files via an XML document containing an external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue.
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Analysis
by VulDB Data Team • 10/04/2022
The vulnerability identified as CVE-2016-7458 represents a critical XML External Entity (XXE) flaw within VMware vSphere Client versions prior to specific security patches. This vulnerability exists in both vSphere Client 5.5 before U3e and 6.0 before U2a, affecting both vCenter Server and ESXi instances. The XXE vulnerability stems from improper input validation in the XML processing components of the vSphere Client, creating a pathway for remote attackers to exploit the system through crafted XML documents. The flaw specifically manifests when the application processes XML documents containing external entity declarations combined with entity references, allowing unauthorized file access on the underlying system. This vulnerability falls under CWE-611, which categorizes improper restriction of XML external entity references as a critical weakness in software applications. The attack vector leverages the client-side XML parser's handling of external entities, enabling an attacker to reference files on the server through carefully constructed XML payloads that exploit the XML processing libraries used by the vSphere Client.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the capability to read arbitrary files from the target system. This includes potentially sensitive configuration files, credential stores, and system files that could contain authentication tokens, database connection strings, or other critical system information. The remote nature of the attack means that an unauthenticated attacker could potentially access files that would normally require local system access or administrative privileges. This vulnerability directly aligns with ATT&CK technique T1566, which covers the exploitation of remote services through XML external entity injection. The affected vSphere Client versions create a persistent threat vector that could be exploited by attackers to gain intelligence about the target environment, potentially leading to further compromise through privilege escalation or lateral movement within the network infrastructure.
Mitigation strategies for CVE-2016-7458 primarily involve applying the vendor-provided security patches for vSphere Client 5.5 U3e and 6.0 U2a releases, which address the XXE vulnerability through proper XML input validation and entity handling. Organizations should implement network segmentation to limit access to vSphere Client services and restrict direct network access to vCenter Server and ESXi hosts. The implementation of XML parser security configurations that disable external entity processing and DTD (Document Type Definition) loading represents a crucial defensive measure. Security teams should also consider implementing web application firewalls that can detect and block suspicious XML content patterns, particularly those containing external entity declarations. Additionally, regular security assessments should verify that XML processing components are properly configured to prevent XXE attacks, and system administrators should monitor for unusual file access patterns that could indicate exploitation attempts. The vulnerability demonstrates the importance of input validation in web applications and highlights the need for comprehensive security testing of XML processing functionalities within enterprise software platforms.