CVE-2017-8559 in Exchange Server
Summary
by MITRE
Microsoft Exchange Server 2010 SP3, Exchange Server 2013 SP3, Exchange Server 2013 CU16, and Exchange Server 2016 CU5 allows an elevation of privilege vulnerability due to the way that Exchange Outlook Web Access (OWA) handles web requests, aka "Microsoft Exchange Cross-Site Scripting Vulnerability". This CVE ID is unique from CVE-2017-8560.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 12/31/2020
The vulnerability identified as CVE-2017-8559 represents a critical elevation of privilege flaw within Microsoft Exchange Server versions 2010 SP3, 2013 SP3, 2013 CU16, and 2016 CU5. This vulnerability specifically affects the Outlook Web Access component of Exchange Server, which serves as the web-based interface for email access and management. The flaw stems from improper handling of web requests within the OWA module, creating a pathway for malicious actors to escalate their privileges within the Exchange environment. This cross-site scripting vulnerability allows attackers to execute arbitrary code with elevated permissions, potentially compromising the entire Exchange infrastructure. The vulnerability is particularly concerning because it affects multiple versions of Exchange Server, creating widespread exposure across enterprise environments that rely on Microsoft's email infrastructure.
The technical implementation of this vulnerability involves the manipulation of web request parameters within the Outlook Web Access interface. When Exchange Server processes certain web requests through OWA, it fails to properly sanitize input data, creating opportunities for attackers to inject malicious scripts or commands. This improper input validation allows threat actors to bypass authentication mechanisms and gain unauthorized access to elevated system privileges. The vulnerability operates at the application layer and can be exploited through web-based attacks, making it accessible to remote attackers without requiring physical access to the server. According to CWE classification, this vulnerability aligns with CWE-79, which describes Cross-Site Scripting flaws, and CWE-20, which covers Improper Input Validation. The attack vector specifically targets the web interface component, making it a prime target for automated exploitation tools and advanced persistent threat actors.
The operational impact of CVE-2017-8559 extends beyond simple privilege escalation to encompass potential complete system compromise. Once an attacker successfully exploits this vulnerability, they can access sensitive email data, modify user accounts, and potentially establish persistent access to the Exchange environment. The elevated privileges gained through this vulnerability enable attackers to manipulate email routing, access confidential communications, and potentially use the compromised Exchange server as a pivot point for attacking other systems within the network. This vulnerability can lead to data breaches, insider threat scenarios, and significant disruption of email services. The impact is particularly severe in environments where Exchange Server serves as the primary email infrastructure, as it provides a direct pathway to sensitive corporate communications and user data. Organizations may experience compliance violations, regulatory penalties, and reputational damage if this vulnerability is exploited successfully.
Mitigation strategies for CVE-2017-8559 should prioritize immediate patch deployment from Microsoft, as the vendor released security updates specifically addressing this vulnerability. Organizations must implement network segmentation to limit access to Exchange servers and apply the appropriate cumulative updates for their Exchange Server versions. Additional protective measures include implementing web application firewalls, conducting regular security assessments, and monitoring for suspicious web requests within the Exchange environment. The implementation of multi-factor authentication and strict access controls can help reduce the potential impact if exploitation occurs. Security teams should also consider deploying intrusion detection systems to monitor for exploitation attempts and maintain detailed audit logs of all Exchange server activities. According to ATT&CK framework, this vulnerability maps to techniques involving privilege escalation and web application attacks, making it essential for organizations to strengthen their defensive posture against these specific threat vectors. Regular security training for administrators and monitoring of web-based attack patterns should be part of comprehensive security programs to prevent successful exploitation of this vulnerability.