CVE-2016-3379 in Exchange
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Microsoft Exchange Server 2016 Cumulative Update 1 and 2 allows remote attackers to inject arbitrary web script or HTML via a meeting-invitation request, aka "Microsoft Exchange Elevation of Privilege Vulnerability."
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Analysis
by VulDB Data Team • 09/16/2022
The vulnerability identified as CVE-2016-3379 represents a critical cross-site scripting flaw within Microsoft Exchange Server 2016 Cumulative Updates 1 and 2. This security weakness enables remote attackers to execute malicious web scripts or HTML code through crafted meeting invitation requests, fundamentally compromising the integrity of the email system. The vulnerability operates at the application layer and specifically targets the handling of calendar invitation data within the Exchange environment, creating a pathway for unauthorized code execution that could potentially escalate privileges within the system.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding mechanisms within Exchange Server's calendar invitation processing functionality. When users receive meeting invitations containing maliciously crafted content, the system fails to properly sanitize the input data before rendering it in the user interface. This processing gap allows attackers to inject script tags or other malicious HTML elements that execute in the context of the victim's browser session. The flaw specifically manifests when Exchange Server processes calendar data, particularly around the rendering of meeting request details, making it particularly dangerous in enterprise environments where calendar sharing and meeting coordination are common practices.
The operational impact of CVE-2016-3379 extends beyond simple script injection, as it creates potential pathways for more severe attacks within the Exchange ecosystem. Attackers could leverage this vulnerability to steal session cookies, redirect users to malicious websites, or even gain elevated privileges within the Exchange environment. The vulnerability's remote exploitation capability means that attackers do not require physical access or network proximity to the Exchange server, making it particularly concerning for organizations with distributed user bases. In enterprise settings, this flaw could enable attackers to compromise user credentials, access sensitive calendar data, or use the compromised system as a staging point for further attacks within the network infrastructure.
Organizations affected by this vulnerability should implement immediate mitigations including applying the relevant Microsoft security updates and patches released following the disclosure. Network segmentation and web application firewalls can provide additional layers of protection by monitoring and filtering suspicious calendar invitation data. Security teams should also implement enhanced monitoring of calendar-related activities and user access patterns to detect potential exploitation attempts. The vulnerability aligns with CWE-79 which categorizes cross-site scripting flaws, and can be mapped to ATT&CK techniques involving initial access through malicious email content and privilege escalation through web-based attacks. Regular security awareness training for users regarding suspicious calendar invitations and implementing proper input validation controls within Exchange Server configurations remain critical defensive measures against this and similar vulnerabilities.