CVE-2016-1000221 in Logstash
Summary
by MITRE
Logstash prior to version 2.3.4, Elasticsearch Output plugin would log to file HTTP authorization headers which could contain sensitive information.
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Analysis
by VulDB Data Team • 10/18/2019
The vulnerability identified as CVE-2016-1000221 affects Logstash versions prior to 2.3.4, specifically within the Elasticsearch Output plugin functionality. This security flaw represents a critical information disclosure issue that occurs during the logging process of HTTP authorization headers. The vulnerability stems from improper handling of authentication credentials within the logging mechanism, where sensitive information contained in HTTP headers gets inadvertently written to log files without adequate sanitization or protection measures. The affected component operates as part of the data processing pipeline in Logstash, which serves as a server-side data processing pipeline that collects, transforms, and forwards data to various destinations including Elasticsearch clusters.
The technical implementation flaw involves the Elasticsearch Output plugin's logging behavior when processing HTTP requests containing authorization headers. When Logstash communicates with Elasticsearch servers, it typically includes authentication tokens, API keys, or other sensitive credentials within HTTP headers. The vulnerability manifests when these headers are logged to file without proper filtering or obfuscation, potentially exposing confidential information such as bearer tokens, basic authentication credentials, or other access control mechanisms. This behavior violates fundamental security principles of least privilege and secure logging practices, as sensitive data flows through the system without appropriate protection measures. The flaw operates at the application level within the logging subsystem, where the plugin fails to implement proper header sanitization before writing to persistent storage.
The operational impact of this vulnerability extends beyond simple information disclosure, as it creates potential attack vectors for unauthorized parties who gain access to Logstash log files. Attackers could extract authentication tokens, API keys, or other sensitive credentials that would allow them to impersonate legitimate users or gain unauthorized access to Elasticsearch clusters and underlying data stores. This vulnerability directly enables credential compromise attacks and can facilitate lateral movement within network environments where Elasticsearch is used for data storage and retrieval. The exposure of HTTP authorization headers in log files creates a persistent threat surface that remains active even after the initial authentication event, as log files may be retained for extended periods and potentially accessed by unauthorized personnel with file system privileges. The vulnerability aligns with CWE-200, which describes improper handling of sensitive information, and represents a failure to implement proper input validation and sanitization in the logging process.
Mitigation strategies for this vulnerability require immediate patching of Logstash installations to version 2.3.4 or later, which contains the necessary fixes to prevent logging of HTTP authorization headers. Organizations should also implement comprehensive log management practices including regular log file access reviews, implementation of log rotation policies, and secure storage mechanisms for sensitive data. Security controls should include monitoring for unauthorized access attempts to log files and implementation of file system permissions that restrict access to sensitive log data. Additionally, organizations should consider implementing log sanitization processes that automatically filter out sensitive information before any data is written to persistent storage. The remediation approach should align with industry best practices outlined in frameworks such as NIST SP 800-92 for log management and the MITRE ATT&CK framework's logging and monitoring categories, ensuring that the vulnerability is addressed through both immediate patching and long-term security process improvements.