CVE-2019-0817 in Exchange Server
Summary
by MITRE
A spoofing vulnerability exists in Microsoft Exchange Server when Outlook Web Access (OWA) fails to properly handle web requests, aka 'Microsoft Exchange Spoofing Vulnerability'. This CVE ID is unique from CVE-2019-0858.
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Analysis
by VulDB Data Team • 05/28/2020
The vulnerability identified as CVE-2019-0817 represents a critical spoofing weakness within Microsoft Exchange Server's Outlook Web Access component that enables attackers to manipulate web request handling processes. This security flaw specifically affects the authentication and authorization mechanisms within the web interface, creating opportunities for malicious actors to impersonate legitimate users or systems. The vulnerability stems from insufficient validation of web requests that pass through the OWA subsystem, allowing unauthorized parties to exploit the system's trust model. Security researchers have classified this issue as a spoofing vulnerability due to its ability to deceive the system into accepting forged or manipulated requests as legitimate communications.
The technical implementation of this vulnerability resides in the improper handling of HTTP requests within the Exchange Server's web infrastructure, particularly affecting the authentication flow between client browsers and the server components. When users access Exchange Server through Outlook Web Access, the system processes various web requests that should be validated against legitimate user credentials and session states. However, the flaw allows attackers to manipulate these requests in ways that bypass normal authentication checks, potentially enabling them to access email accounts, modify settings, or impersonate authorized users. This weakness operates at the application layer of the OSI model, specifically within the web application security controls that govern user access and session management. The vulnerability is categorized under CWE-287 which addresses improper handling of authentication tokens and session identifiers, making it particularly dangerous for email server environments where user credentials are continuously validated.
The operational impact of CVE-2019-0817 extends significantly beyond simple spoofing capabilities, as it can enable attackers to establish persistent access to Exchange Server environments and potentially escalate privileges within the organization's email infrastructure. Once exploited, this vulnerability allows adversaries to access sensitive email communications, modify user account settings, and potentially gain access to additional system resources through the compromised Exchange Server. The attack surface is particularly concerning given that Exchange Server typically serves as a central communication hub for enterprise organizations, making successful exploitation a significant threat to business continuity and data security. Organizations with Exchange Server deployments are at risk of unauthorized email access, potential data exfiltration, and the establishment of backdoors through the compromised web interface. The vulnerability's exploitation can occur without requiring advanced technical skills or privileged access, making it particularly attractive to threat actors seeking to gain unauthorized access to corporate email systems.
Mitigation strategies for CVE-2019-0817 should prioritize immediate implementation of Microsoft's security patches and updates, as the vulnerability affects core Exchange Server functionality that requires prompt remediation. Organizations must ensure that their Exchange Server environments are updated with the latest security patches released by Microsoft, particularly focusing on the OWA authentication modules and web request handling components. Network segmentation and access controls should be strengthened to limit exposure of Exchange Server components to untrusted networks, while implementing additional monitoring for suspicious authentication patterns and web request anomalies. Security teams should also consider implementing multi-factor authentication for Exchange Server access, as this adds additional layers of protection beyond traditional username and password authentication. The vulnerability's classification under ATT&CK technique T1566, which covers phishing and social engineering attacks, indicates that organizations should enhance their email security measures and user awareness training to prevent initial compromise. Regular security audits and penetration testing of Exchange Server environments should be conducted to identify potential exploitation vectors, while network traffic monitoring should be enhanced to detect anomalous behavior patterns associated with spoofing attacks.