CVE-2015-1632 in Exchange Server
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in errorfe.aspx in Outlook Web App (OWA) in Microsoft Exchange Server 2013 SP1 and Cumulative Update 7 allows remote attackers to inject arbitrary web script or HTML via the msgParam parameter in an authError action, aka "Exchange Error Message Cross Site Scripting Vulnerability."
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Analysis
by VulDB Data Team • 04/15/2022
The vulnerability identified as CVE-2015-1632 represents a critical cross-site scripting flaw within Microsoft Exchange Server's Outlook Web App component. This security weakness exists in the errorfe.aspx page which handles authentication errors in Exchange Server 2013 SP1 and Cumulative Update 7 environments. The vulnerability specifically affects the authentication error handling mechanism where user-supplied input is not properly sanitized before being rendered in web responses. Attackers can exploit this weakness by crafting malicious payloads through the msgParam parameter within authError actions, enabling them to inject arbitrary web scripts or HTML content that executes in the context of authenticated users' browsers.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding practices within the Outlook Web App error handling routines. When the system encounters authentication failures, it processes the msgParam parameter without sufficient sanitization measures, allowing malicious code to persist in the error messages displayed to users. This flaw operates at the application layer and leverages the trust relationship between the user's browser and the Exchange server, making it particularly dangerous as it can be exploited without requiring authentication credentials. The vulnerability specifically maps to CWE-79 which defines Cross-Site Scripting as a weakness where applications fail to properly encode or validate user-provided data before incorporating it into web responses.
The operational impact of this vulnerability extends beyond simple script injection, potentially enabling attackers to perform session hijacking, steal user credentials, or redirect victims to malicious websites. An attacker could craft a phishing attack that appears legitimate to users accessing Exchange Web Services, as the malicious script would execute within the trusted context of the Outlook Web App interface. This creates a significant risk for enterprise environments where Exchange servers handle sensitive corporate communications, as successful exploitation could lead to unauthorized access to email accounts, calendar data, and contact information. The vulnerability particularly affects organizations running Exchange Server 2013 with the specified updates, making it a widespread concern for enterprises maintaining legacy Exchange infrastructure.
Mitigation strategies for CVE-2015-1632 should include immediate application of Microsoft's security patches and updates, particularly the cumulative updates released to address this specific vulnerability. Organizations should also implement web application firewalls to filter malicious input parameters and establish robust input validation mechanisms within their Exchange environments. Network segmentation and monitoring should be enhanced to detect suspicious authentication error patterns that might indicate exploitation attempts. Security teams should conduct regular vulnerability assessments and penetration testing to identify similar weaknesses in related components. Additionally, user education regarding phishing awareness and suspicious email behaviors remains crucial, as attackers may leverage this vulnerability as part of broader social engineering campaigns. The remediation process should align with industry best practices outlined in the MITRE ATT&CK framework, particularly focusing on defenses against credential access and execution techniques that could be employed through this XSS vulnerability.