CVE-2017-6821 in Zimbra Collaboration
Summary
by MITRE
Directory traversal vulnerability in Zimbra Collaboration Suite (aka ZCS) before 8.7.6 allows attackers to have unspecified impact via unknown vectors.
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Analysis
by VulDB Data Team • 02/03/2020
The directory traversal vulnerability identified as CVE-2017-6821 affects the Zimbra Collaboration Suite version 8.7.5 and earlier, representing a critical security flaw that enables unauthorized access to sensitive system resources. This vulnerability resides within the Zimbra Collaboration Suite's handling of file paths and directory references, creating a pathway for malicious actors to bypass normal access controls and potentially gain unauthorized system access. The vulnerability's impact extends beyond simple file access as it can be leveraged to execute arbitrary code or extract confidential information from the affected system. The specific attack vectors remain unspecified in the CVE description, which is common for vulnerabilities where the exact exploitation methods are not fully disclosed or understood by the reporting authorities at the time of classification.
The technical implementation of this directory traversal flaw demonstrates a classic weakness in input validation and path handling within the Zimbra application framework. Attackers can manipulate file path parameters to navigate beyond the intended directory boundaries and access restricted files or directories that should normally be protected. This type of vulnerability typically occurs when applications fail to properly sanitize user-supplied input before using it in file system operations. The flaw allows for path traversal attacks where malicious users can exploit relative path references such as ../ or ..\ to move up directory levels and access files outside of the application's designated working directory. The vulnerability's classification under CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) indicates a fundamental failure in implementing proper access controls and input validation mechanisms. This weakness directly impacts the application's ability to maintain proper security boundaries and can be exploited to access configuration files, user data, or system binaries that contain sensitive information.
From an operational perspective, the impact of CVE-2017-6821 can be severe for organizations relying on Zimbra Collaboration Suite for email and collaboration services. The vulnerability creates a potential attack surface that could allow threat actors to extract user credentials, email content, system configurations, or other sensitive data stored within the Zimbra environment. Depending on the system's configuration and the privileges associated with the affected components, attackers might be able to escalate their privileges or even gain remote code execution capabilities. The unspecified nature of the impact in the CVE description suggests that depending on the specific environment and implementation details, the vulnerability could lead to various outcomes including data exfiltration, system compromise, or service disruption. Organizations using affected versions of Zimbra are particularly vulnerable as the flaw exists in core file handling functionality that is essential for the application's operation.
Security professionals should consider this vulnerability in relation to the MITRE ATT&CK framework, specifically mapping it to techniques involving privilege escalation and credential access. The vulnerability's exploitation aligns with ATT&CK technique T1078 (Valid Accounts) and T1566 (Phishing) as attackers might leverage this flaw to obtain credentials or escalate privileges within the compromised environment. Additionally, the vulnerability's potential for remote code execution places it within the context of T1059 (Command and Scripting Interpreter) and T1041 (Exfiltration) techniques. Organizations should implement immediate mitigation strategies including updating to Zimbra Collaboration Suite version 8.7.6 or later, which contains the necessary patches to address this vulnerability. Network segmentation and monitoring of file access patterns can help detect potential exploitation attempts. Regular security assessments and vulnerability scanning should include checks for this specific vulnerability, as it represents a persistent risk for organizations that have not yet updated their systems. The vulnerability also underscores the importance of maintaining current security patches and implementing robust input validation controls throughout the application lifecycle to prevent similar issues from occurring in other components of the system.