CVE-2015-2544 in Exchange Server
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Outlook Web Access (OWA) in Microsoft Exchange Server 2013 Cumulative Update 8 and 9 and SP1 allows remote attackers to inject arbitrary web script or HTML via a crafted e-mail message, aka "Exchange Spoofing Vulnerability."
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 06/14/2022
The CVE-2015-2544 vulnerability represents a critical cross-site scripting flaw within Microsoft Exchange Server's Outlook Web Access component, specifically affecting versions 2013 with Cumulative Updates 8 and 9, as well as Service Pack 1. This vulnerability operates under the Common Weakness Enumeration identifier CWE-79 which categorizes it as a classic cross-site scripting weakness where untrusted data is improperly incorporated into web page content without adequate sanitization or encoding. The flaw enables remote attackers to execute malicious scripts within the context of a victim's browser session, potentially compromising user security and data integrity.
The technical implementation of this vulnerability occurs through the manipulation of email message content within the Outlook Web Access interface. Attackers can craft specially formatted email messages containing malicious script code that gets executed when the targeted user views the compromised email within the OWA environment. This spoofing mechanism exploits the lack of proper input validation and output encoding in the web interface's handling of email content, allowing attackers to inject arbitrary HTML and JavaScript code that persists in the user's browser session. The vulnerability specifically targets the rendering pipeline of email messages within the web client, bypassing traditional email security measures that might otherwise prevent such malicious content.
The operational impact of this vulnerability extends beyond simple script execution, creating significant risks for enterprise environments where Exchange Server serves as a primary communication platform. Successful exploitation could enable attackers to steal session cookies, perform unauthorized actions on behalf of users, access sensitive corporate data, or establish persistent backdoors within the organization's email infrastructure. The remote nature of the attack means that threat actors can target users from external networks without requiring physical access or prior authentication to the Exchange server itself. This vulnerability directly aligns with ATT&CK technique T1566 which describes social engineering tactics involving the delivery of malicious content through email, and T1059 which encompasses the execution of malicious code through web-based interfaces.
Organizations affected by this vulnerability face substantial security implications, particularly in environments where users regularly access Exchange through web browsers and where email remains a primary vector for enterprise attacks. The vulnerability's presence in both Cumulative Update versions and Service Pack 1 indicates a widespread exposure across multiple supported configurations, making it a high-priority remediation target for security teams. The attack surface is particularly concerning given that OWA serves as a web-based interface for email access, making it a prime target for phishing campaigns and social engineering attacks that leverage the trust users place in legitimate email communications. Security professionals must consider this vulnerability as part of broader email security strategies, implementing additional layers of protection beyond the standard patch management processes.
Mitigation strategies for CVE-2015-2544 should include immediate deployment of Microsoft security patches addressing the specific XSS vulnerability in Exchange Server 2013. Organizations should also implement additional security controls such as web application firewalls that can detect and block malicious script injection attempts, enhanced email filtering solutions that can identify and quarantine suspicious email content, and user education programs that emphasize the dangers of opening untrusted email messages. Network segmentation and access controls should be reviewed to limit exposure of Exchange servers to untrusted networks, while regular security assessments should verify that the implemented mitigations are effective against similar vulnerabilities. The remediation process should also include monitoring for indicators of compromise and establishing incident response procedures specifically designed to handle email-based attack vectors.