CVE-2016-6189 in SOGo
Summary
by MITRE
Incomplete blacklist in SOGo before 2.3.12 and 3.x before 3.1.1 allows remote authenticated users to obtain sensitive information by reading the fields in the (1) ics or (2) XML calendar feeds.
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Analysis
by VulDB Data Team • 08/15/2020
The vulnerability identified as CVE-2016-6189 represents a critical information disclosure flaw in SOGo, a web-based groupware server that provides calendaring and email services. This issue affects versions prior to 2.3.12 and 3.x prior to 3.1.1, where the application fails to properly validate or filter user input when processing calendar feeds. The vulnerability stems from an incomplete blacklist implementation that does not adequately restrict access to sensitive data within calendar feeds, specifically those formatted in ics (iCalendar) or XML structures. The flaw allows authenticated attackers to exploit this weakness and extract confidential information that should remain protected within the system.
The technical nature of this vulnerability aligns with CWE-200, which addresses improper exposure of sensitive information, and represents a classic case of insufficient input validation and access control. When SOGo processes calendar feeds, particularly those containing ics or XML formatted data, the application fails to properly sanitize or filter user-supplied content. This incomplete blacklist mechanism means that certain field names or data structures within calendar feeds can be accessed by unauthorized users who have authenticated access to the system. The vulnerability specifically targets the processing of calendar data where sensitive information may be embedded within field structures, allowing attackers to read fields that should remain confidential.
From an operational perspective, this vulnerability poses significant risks to organizations relying on SOGo for calendar and scheduling services. The impact extends beyond simple data exposure, as calendar feeds often contain sensitive information such as meeting details, personal schedules, and potentially confidential business communications. An authenticated attacker could leverage this vulnerability to gain unauthorized access to calendar data that might include private meetings, sensitive business discussions, or personal information about employees. The fact that this affects both version 2.x and 3.x branches indicates a widespread issue within the SOGo ecosystem, potentially affecting numerous organizations that have not yet updated their systems to the patched versions.
The exploitation of this vulnerability follows patterns consistent with ATT&CK technique T1074.001, which involves data staging through the use of external remote services. Attackers would typically need to first authenticate to the SOGo system to gain access to calendar feeds, then manipulate the ics or XML calendar data to extract sensitive fields. The security implications extend to potential compliance violations, particularly in regulated environments where calendar data may contain personally identifiable information or confidential business data. Organizations implementing SOGo should consider this vulnerability as part of their broader security posture assessment, particularly in relation to information disclosure controls and data protection requirements.
Organizations should immediately implement mitigations including updating to SOGo versions 2.3.12 or 3.1.1, which contain the necessary fixes for this vulnerability. Additional protective measures should include implementing stricter access controls for calendar feeds, monitoring for unauthorized access attempts, and conducting regular security assessments of calendar and scheduling systems. The vulnerability highlights the importance of proper input validation and access control mechanisms, particularly in applications that process structured data formats like ics and XML. Security teams should also consider implementing network segmentation and monitoring to detect potential exploitation attempts, as the vulnerability requires authenticated access but can lead to significant information disclosure.