CVE-2015-8489 in Office
Summary
by MITRE
customapp in Cybozu Office 9.9.0 through 10.3.0 allows remote authenticated users to cause a denial of service (excessive database locking) via a crafted CSV file, a different vulnerability than CVE-2016-1153.
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Analysis
by VulDB Data Team • 07/30/2018
The vulnerability identified as CVE-2015-8489 affects Cybozu Office versions 9.9.0 through 10.3.0 and represents a significant denial of service weakness in the customapp component. This flaw enables remote authenticated attackers to disrupt system operations by exploiting database locking mechanisms through the manipulation of CSV file inputs. The vulnerability specifically targets the processing of structured data files within the application's custom application framework, creating a scenario where legitimate database operations become severely impacted due to excessive locking behavior. Unlike CVE-2016-1153 which addresses a different aspect of the same software, this vulnerability focuses exclusively on the database locking mechanism during CSV import processes.
The technical implementation of this vulnerability occurs when the customapp component processes specially crafted CSV files that contain specific formatting or data patterns designed to trigger excessive database locking operations. When such malicious CSV files are imported into the Cybozu Office environment, the application's internal database management system becomes overwhelmed with lock requests, causing legitimate database transactions to queue indefinitely or fail entirely. This excessive locking behavior stems from improper resource management within the CSV parsing logic, where the system fails to properly release database locks after processing individual records or batches. The flaw essentially creates a resource exhaustion condition that manifests as denial of service rather than system compromise, though the impact on operational availability remains severe.
From an operational perspective, this vulnerability presents a critical risk to organizations relying on Cybozu Office for business processes, as it allows attackers with valid authentication credentials to render the application unusable for legitimate users. The denial of service condition affects database connectivity and application responsiveness, potentially disrupting workflows that depend on custom applications and data processing capabilities. Attackers can exploit this vulnerability repeatedly without requiring additional authentication, making it particularly dangerous in environments where users maintain persistent access to the system. The impact extends beyond simple service disruption to potentially affecting business continuity and productivity, especially in scenarios where database operations are critical for application functionality.
Organizations should implement immediate mitigations including restricting CSV import capabilities for non-privileged users, implementing input validation and sanitization for CSV files, and monitoring database lock patterns for unusual activity. System administrators should consider upgrading to patched versions of Cybozu Office where available, as this vulnerability was addressed in subsequent releases. Network segmentation and access controls can help limit the potential impact by restricting which users can access the customapp functionality. Additionally, implementing database monitoring tools that can detect excessive locking behavior and alert administrators to potential exploitation attempts provides an additional layer of defense. The vulnerability aligns with CWE-400, which categorizes excessive resource consumption as a significant security concern, and represents a specific implementation weakness in database transaction management that could be exploited through the ATT&CK technique of resource hijacking to disrupt service availability.