CVE-2015-1631 in Exchange Server
Summary
by MITRE
Microsoft Exchange Server 2013 SP1 and Cumulative Update 7 allows remote attackers to spoof meeting organizers via unspecified vectors, aka "Exchange Forged Meeting Request Spoofing Vulnerability."
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Analysis
by VulDB Data Team • 04/15/2022
The CVE-2015-1631 vulnerability represents a significant security flaw in Microsoft Exchange Server 2013 SP1 and Cumulative Update 7 that enables remote attackers to manipulate calendar meeting requests and impersonate legitimate organizers. This vulnerability specifically targets the Exchange Server's handling of meeting invitations and calendar data, creating a spoofing vector that can be exploited without requiring authentication or direct system access. The flaw exists within the server's calendar processing mechanisms and allows attackers to forge meeting requests that appear to originate from trusted users or organizations, potentially leading to social engineering attacks and unauthorized access to calendar data.
The technical implementation of this vulnerability stems from insufficient validation and authentication checks within Exchange Server's calendar request processing pipeline. When meeting invitations are received and processed by the server, the system fails to properly verify the authenticity of the organizer information, allowing malicious actors to manipulate the organizer field in calendar entries. This weakness can be exploited through various attack vectors including email manipulation, direct server interaction, or by leveraging other compromised systems within the network. The vulnerability specifically affects the Exchange Server's calendar synchronization and distribution mechanisms, where meeting requests are processed and distributed to attendees.
From an operational impact perspective, this vulnerability creates substantial risks for enterprise environments that rely heavily on Exchange Server for calendar management and scheduling. Attackers can exploit this flaw to send forged meeting requests that appear to come from executives, IT personnel, or other trusted individuals, potentially leading to unauthorized access to sensitive meetings, data breaches, or phishing campaigns. The spoofing capability extends beyond simple calendar manipulation to potentially enable more sophisticated attacks such as credential harvesting, unauthorized access to meeting resources, or disruption of business operations through false scheduling information. Organizations may experience significant damage to their security posture, as this vulnerability undermines the trust model of calendar-based communications and can facilitate broader compromise attempts.
The vulnerability aligns with CWE-287, which addresses improper authentication issues in software systems, and maps to several ATT&CK techniques including T1566 for spearphishing with social engineering and T1078 for valid accounts. Organizations should implement immediate mitigations including applying the relevant Microsoft security updates, implementing additional email filtering rules to detect suspicious calendar invitations, and monitoring calendar access patterns for unusual activity. Network segmentation and enhanced email security controls can help reduce the attack surface, while user education about calendar-based social engineering attacks remains crucial. The vulnerability also highlights the importance of proper input validation and authentication mechanisms in enterprise messaging systems, particularly those handling sensitive scheduling and organizational data.