CVE-2016-6188 in SOGo
Summary
by MITRE
Memory leak in SOGo 2.3.7 allows remote attackers to cause a denial of service (memory consumption) via a large number of attempts to upload a large attachment, related to temporary files.
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Analysis
by VulDB Data Team • 11/11/2022
The vulnerability identified as CVE-2016-6188 represents a critical memory leak issue within SOGo version 2.3.7, a web-based groupware server that provides email, calendar, and collaboration services. This flaw specifically manifests when the system processes multiple concurrent requests involving large file uploads, creating a condition where temporary files are not properly cleaned up or released from memory. The issue stems from inadequate resource management within the attachment handling mechanisms, allowing attackers to exploit the system's memory allocation patterns through repeated upload attempts.
The technical implementation of this vulnerability involves the improper handling of temporary file storage during the attachment upload process. When SOGo receives large attachment requests, it creates temporary files to store the data before final processing. However, in version 2.3.7, these temporary files remain allocated in memory even after the upload process completes or fails, leading to progressive memory consumption. The flaw is particularly dangerous because it can be exploited remotely without requiring authentication, making it accessible to any attacker with network access to the affected server. The memory leak occurs incrementally with each failed or successful upload attempt, causing the system to gradually consume available memory resources until the server becomes unresponsive or crashes.
From an operational impact perspective, this vulnerability creates a significant denial of service condition that can severely impact business continuity and collaboration services. Organizations relying on SOGo for email and calendar services face potential downtime when attackers systematically exploit this memory leak through multiple upload attempts. The vulnerability can be amplified through automated tools that rapidly initiate upload requests, allowing attackers to consume system resources within minutes. The impact extends beyond simple service disruption, as the memory exhaustion can affect other processes running on the same server, potentially causing cascading failures across the entire infrastructure. This type of vulnerability directly violates security principles outlined in the OWASP Top Ten, particularly focusing on resource exhaustion and inadequate error handling.
The vulnerability aligns with CWE-401, which specifically addresses improper release of memory resources, and can be mapped to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion. Organizations should implement immediate mitigations including upgrading to SOGo version 2.3.8 or later, which contains the necessary patches to address the memory leak issue. Additionally, administrators should implement rate limiting on file upload operations, monitor memory consumption patterns, and configure automated alerting for unusual resource usage. Network-level protections such as firewall rules limiting upload sizes and implementing connection throttling can provide additional defense in depth. The vulnerability also highlights the importance of proper input validation and resource cleanup procedures, emphasizing the need for thorough testing of file handling components and implementation of automated memory monitoring systems to detect and prevent similar issues in other applications.