CVE-2015-8484 in Office
Summary
by MITRE
Cybozu Office 9.9.0 through 10.3.0 allows remote authenticated users to bypass intended calendar-viewing restrictions via unspecified vectors, a different vulnerability than CVE-2015-8485, CVE-2015-8486, and CVE-2016-1152.
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Analysis
by VulDB Data Team • 07/30/2018
The vulnerability identified as CVE-2015-8484 affects Cybozu Office versions 9.9.0 through 10.3.0, representing a significant authorization bypass issue that undermines the intended security controls for calendar access. This flaw specifically targets the calendar viewing restrictions that should prevent authenticated users from accessing calendar data they are not authorized to view, creating a pathway for unauthorized information disclosure. The vulnerability operates at the application level where access control mechanisms fail to properly validate user permissions when accessing calendar resources, allowing attackers to circumvent the established security boundaries that should protect sensitive scheduling information.
The technical implementation of this vulnerability appears to stem from insufficient input validation and access control checks within the calendar module of Cybozu Office. When authenticated users attempt to view calendar entries, the system should verify their permissions against the calendar owner's access control lists and user roles. However, the flaw enables attackers to manipulate request parameters or exploit specific code paths that bypass these validation mechanisms, effectively allowing them to access calendar data belonging to other users within the same organization. This represents a classic access control vulnerability that aligns with CWE-285, which addresses improper authorization in software systems. The vulnerability's classification as an authorization bypass indicates that it operates at the application logic level rather than through network-level attacks or direct system exploitation.
The operational impact of this vulnerability extends beyond simple information disclosure, as calendar data often contains sensitive business information including meeting schedules, project timelines, resource allocations, and personal details of employees. Attackers who exploit this vulnerability can gain unauthorized access to confidential scheduling information that may reveal business strategies, internal communications, or personal employee details. The fact that this vulnerability affects multiple versions of the software suggests it was likely introduced during a specific development cycle and remained undetected for an extended period. Organizations using Cybozu Office in enterprise environments face significant risks as this vulnerability could enable adversaries to gather intelligence about business operations, identify key personnel, and potentially plan targeted attacks based on scheduling patterns and resource availability.
Security professionals should note that this vulnerability operates independently from other calendar-related flaws such as CVE-2015-8485, CVE-2015-8486, and CVE-2016-1152, indicating that the security issues in Cybozu Office's calendar functionality were extensive and multifaceted. The vulnerability's exploitation requires authentication, meaning attackers must first obtain valid user credentials before attempting to bypass calendar restrictions, but this still represents a significant security gap in the application's permission model. Organizations should implement immediate mitigations including updating to patched versions of Cybozu Office, reviewing calendar access controls, and monitoring for unauthorized access attempts. The ATT&CK framework would classify this vulnerability under privilege escalation and credential access tactics, as it enables attackers to expand their access within the system beyond their initially granted permissions.
Organizations should also consider implementing additional security controls such as network segmentation, enhanced logging and monitoring of calendar access patterns, and regular security assessments of collaboration platforms. The vulnerability demonstrates the critical importance of proper access control implementation in business applications and the potential for seemingly minor authorization flaws to create significant security risks. Regular vulnerability assessments and security audits of enterprise collaboration tools remain essential to identify and remediate similar access control weaknesses that could be exploited by malicious actors. The complexity of modern enterprise applications means that vulnerabilities like CVE-2015-8484 highlight the need for comprehensive security testing throughout the software development lifecycle to prevent such authorization bypass issues from reaching production environments.