CVE-2020-6938 in Tableau Server
Summary
by MITRE
A sensitive information disclosure vulnerability in Tableau Server 10.5, 2018.x, 2019.x, 2020.x released before June 26, 2020, could allow access to sensitive information in log files.
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Analysis
by VulDB Data Team • 07/09/2020
The vulnerability identified as CVE-2020-6938 represents a critical sensitive information disclosure flaw within Tableau Server versions spanning 10.5 through 2020.x, specifically affecting releases prior to the June 26, 2020 security patch. This vulnerability stems from inadequate log file management practices where sensitive data becomes inadvertently exposed through log file contents, creating potential attack vectors for malicious actors seeking to extract confidential information from affected systems. The flaw manifests when the server generates log entries that contain unredacted sensitive data such as authentication tokens, user credentials, or other proprietary information, which should never be persisted in plaintext within log files.
From a technical perspective, this vulnerability operates through improper input sanitization and output handling mechanisms within the Tableau Server logging subsystem. The system fails to adequately filter or redact sensitive information before writing it to log files, allowing attackers who gain access to these files to obtain potentially valuable credentials or system information. This type of vulnerability aligns with CWE-200, which specifically addresses improper exposure of sensitive information, and represents a classic case of information leakage through insecure logging practices. The vulnerability is particularly concerning because log files often contain detailed system information including user activities, system configurations, and authentication attempts that can provide attackers with comprehensive insights into the target environment.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates opportunities for privilege escalation and further attack progression within compromised environments. Attackers who can access these log files may extract session tokens, API keys, or other authentication mechanisms that could lead to unauthorized access to Tableau Server resources and potentially to underlying data sources. The vulnerability's persistence across multiple versions indicates a systemic issue in the logging implementation that could have remained undetected for extended periods, providing attackers with prolonged opportunities to exploit the flaw. This issue particularly affects organizations that maintain extensive logging practices or those with inadequate log file access controls, where unauthorized personnel might gain access to sensitive data through log file enumeration or misconfigurations.
Security professionals should implement immediate mitigations including comprehensive log file access controls, regular log file audits, and the implementation of log redaction policies that prevent sensitive data from being written to persistent storage. Organizations must ensure that log files are stored with appropriate permissions and that automated systems are deployed to scan and remove sensitive information before logging occurs. The remediation process should include applying the June 26, 2020 security patches released by Tableau, which address the root cause through improved input validation and logging sanitization mechanisms. Additionally, implementing the principle of least privilege for log file access and establishing regular monitoring procedures for unauthorized log file access attempts can significantly reduce the risk of exploitation. This vulnerability demonstrates the critical importance of secure logging practices and aligns with ATT&CK technique T1070.002, which covers the use of log files for information gathering and reconnaissance activities, emphasizing the need for comprehensive log management strategies in enterprise security frameworks.