CVE-2023-26595 in Garoon
Summary
by MITRE • 05/23/2023
Denial-of-service (DoS) vulnerability in Message of Cybozu Garoon 4.10.0 to 5.9.2 allows a remote authenticated attacker to cause a denial of service condition.
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Analysis
by VulDB Data Team • 11/10/2025
The vulnerability identified as CVE-2023-26595 represents a critical denial-of-service flaw affecting Cybozu Garoon versions 4.10.0 through 5.9.2. This issue manifests as a remote authenticated attack vector that enables adversaries with valid credentials to disrupt system availability and compromise service integrity. The affected application serves as a collaboration platform that handles various messaging and calendar functions, making this vulnerability particularly concerning for organizations relying on its continuous operation. The vulnerability falls under the category of CWE-400, which specifically addresses unchecked resource consumption, and aligns with ATT&CK technique T1499.004 for network denial of service attacks. Organizations utilizing this platform face potential operational disruptions that could impact business continuity and collaborative workflows.
The technical implementation of this vulnerability stems from insufficient input validation and resource management within the message processing subsystem of Cybozu Garoon. When authenticated users submit specially crafted messages or requests, the system fails to properly handle the malformed inputs, leading to resource exhaustion or application crashes. This flaw demonstrates poor error handling mechanisms and inadequate bounds checking in the message parsing routines. The vulnerability exploits the legitimate authentication pathways within the system, making it particularly dangerous as it requires minimal privileges beyond valid user credentials. Attackers can leverage this weakness to repeatedly submit malicious payloads that consume system resources, ultimately causing the application to become unresponsive or terminate unexpectedly.
The operational impact of CVE-2023-26595 extends beyond simple service disruption to encompass broader business continuity concerns and potential data integrity issues. Organizations relying on Garoon for critical communication and scheduling functions may experience significant downtime that affects productivity and collaboration across departments. The vulnerability's remote nature means attackers can exploit it from external networks without requiring physical access to the system, increasing the attack surface and reducing the effectiveness of traditional perimeter-based security measures. Furthermore, the authenticated nature of the attack implies that compromised user accounts could be weaponized to cause denial-of-service conditions, creating a cascading effect that could impact multiple users and services within the platform. This vulnerability directly violates the availability principles of the CIA triad and can be categorized under ATT&CK tactic TA0040 for denial of service.
Mitigation strategies for CVE-2023-26595 should prioritize immediate patch deployment from Cybozu, as this represents the most effective solution to address the root cause of the vulnerability. Organizations should implement network-level controls such as rate limiting and connection throttling to limit the impact of potential attacks while awaiting patches. Monitoring and logging mechanisms should be enhanced to detect unusual patterns of message processing that might indicate exploitation attempts. Security teams should conduct thorough access reviews to ensure that only necessary users have elevated privileges that could be exploited. Additionally, implementing network segmentation and firewall rules to restrict access to the Garoon application can reduce the attack surface. Regular security assessments and penetration testing should be performed to identify similar vulnerabilities in the broader application ecosystem, while incident response procedures should be updated to address potential denial-of-service scenarios involving this platform.