CVE-2017-11932 in Exchange Server
Summary
by MITRE
Microsoft Exchange Server 2016 CU5 and Microsoft Exchange Server 2016 CU5 allow a spoofing vulnerability due to the way Outlook Web Access (OWA) validates web requests, aka "Microsoft Exchange Spoofing Vulnerability".
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Analysis
by VulDB Data Team • 01/27/2021
The Microsoft Exchange Server 2016 CU5 contains a spoofing vulnerability within its Outlook Web Access component that enables attackers to manipulate web request validation mechanisms. This vulnerability specifically affects the authentication and authorization processes within the OWA interface, creating opportunities for malicious actors to impersonate legitimate users or systems. The flaw stems from insufficient validation of web requests that traverse the Exchange Server infrastructure, allowing unauthorized parties to exploit the system's trust model and potentially gain elevated privileges or access to sensitive information.
This vulnerability represents a critical security weakness in the web-based email access functionality of Exchange Server, where the system fails to properly verify the authenticity of incoming requests. The spoofing mechanism allows attackers to manipulate headers, session identifiers, or other authentication tokens that should normally be validated before granting access to email services. The issue specifically impacts the way OWA handles web requests, which is a core component of Exchange Server's web interface that enables users to access their email through standard web browsers. According to CWE-345, this vulnerability falls under the category of "Insufficient Verification of Data Authenticity," which is a well-documented weakness that can lead to various forms of authentication bypass and privilege escalation attacks.
The operational impact of this vulnerability extends beyond simple spoofing scenarios to potentially enable more sophisticated attacks within the Exchange environment. An attacker who successfully exploits this vulnerability could gain access to user mailboxes, intercept email communications, modify email content, or even escalate privileges to administrative levels within the Exchange Server infrastructure. The attack surface is particularly concerning given that OWA serves as the primary web interface for many organizations, making this vulnerability potentially accessible to a wide range of threat actors. This weakness can be leveraged as a stepping stone for broader network infiltration, as Exchange Server often serves as a critical communication hub within enterprise environments.
Security professionals should implement immediate mitigations including applying the official Microsoft security patches released for Exchange Server 2016 CU5, which address the specific validation flaws in the OWA component. Network segmentation and access controls should be strengthened around Exchange Server infrastructure to limit exposure, while monitoring systems should be enhanced to detect anomalous authentication patterns or unusual request behaviors that might indicate exploitation attempts. The vulnerability aligns with ATT&CK technique T1566, which covers social engineering methods that can be used to exploit such authentication weaknesses in web applications. Organizations should also consider implementing additional security layers such as multi-factor authentication, enhanced logging mechanisms, and regular security assessments to identify and remediate similar vulnerabilities across their email infrastructure.