CVE-2015-1628 in Exchange Server
Summary
by MITRE
Cross-site scripting (XSS) vulnerability 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 a crafted X-OWA-Canary cookie in an AD.RecipientType.User action, aka "OWA Modified Canary Parameter Cross Site Scripting Vulnerability."
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Analysis
by VulDB Data Team • 04/15/2022
The CVE-2015-1628 vulnerability represents a critical cross-site scripting flaw discovered in Microsoft Exchange Server 2013 SP1 and Cumulative Update 7 within the Outlook Web App component. This vulnerability specifically targets the handling of the X-OWA-Canary cookie parameter during AD.RecipientType.User actions, creating a pathway for remote attackers to execute malicious web scripts or HTML content within the context of authenticated user sessions. The flaw exploits the insufficient input validation and output sanitization mechanisms that govern how OWA processes certain cookie values, particularly those related to the canary parameter used for security monitoring and session validation.
The technical implementation of this vulnerability leverages the fact that the X-OWA-Canary cookie value is not properly sanitized before being rendered in the web application's response. When an attacker crafts a malicious cookie value containing script tags or HTML content and submits it through an AD.RecipientType.User action, the vulnerable OWA component fails to adequately escape or filter the input, allowing the malicious code to execute in the browser context of any user who processes the affected cookie. This behavior aligns with CWE-79, which categorizes cross-site scripting vulnerabilities as weaknesses in input validation and output sanitization, specifically targeting the improper handling of untrusted data in web applications. The vulnerability operates at the application layer and can be exploited without requiring authentication to the target system, though successful exploitation typically requires the victim to interact with a maliciously crafted link or page that sets the vulnerable cookie.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with the capability to perform session hijacking, steal user credentials, access sensitive email content, and potentially escalate privileges within the Exchange environment. Attackers could leverage this vulnerability to establish persistent access to user mailboxes, monitor email communications, and execute further attacks against internal network resources. The vulnerability's presence in Exchange Server 2013 SP1 and Cumulative Update 7 creates a significant risk for organizations that have not applied the necessary security patches, as it affects the core web-based email access functionality that many enterprises depend upon for daily operations. The attack vector is particularly concerning because it can be initiated through standard web browser interactions, making it difficult to detect and prevent without proper security monitoring in place. According to ATT&CK framework, this vulnerability maps to T1566.001 (Phishing: Spearphishing Attachment) and T1059.001 (Command and Scripting Interpreter: Visual Basic), as attackers can use the XSS capability to deliver malicious payloads and execute commands through compromised user sessions.
Organizations should implement immediate mitigations including applying the relevant Microsoft security updates and patches released for Exchange Server 2013 SP1 and Cumulative Update 7 to address the root cause of the vulnerability. Network-based mitigations such as web application firewalls and cookie security policies can provide additional protection layers, though they should not be considered as primary defenses. Security monitoring should be enhanced to detect unusual cookie values and suspicious user behavior patterns that may indicate exploitation attempts. The vulnerability highlights the importance of maintaining current security patches and implementing proper input validation across all web application components. Organizations should also consider implementing Content Security Policy headers and strict cookie security attributes to reduce the impact of similar vulnerabilities in the future. Regular security assessments and penetration testing of Exchange environments are essential to identify and remediate similar weaknesses that could provide attackers with unauthorized access to sensitive email infrastructure.