CVE-2023-23933 in Anomaly Detection
Summary
by MITRE • 02/03/2023
OpenSearch Anomaly Detection identifies atypical data and receives automatic notifications. There is an issue with the application of document and field level restrictions in the Anomaly Detection plugin, where users with the Anomaly Detector role can read aggregated numerical data (e.g. averages, sums) of fields that are otherwise restricted to them. This issue only affects authenticated users who were previously granted read access to the indexes containing the restricted fields. This issue has been patched in versions 1.3.8 and 2.6.0. There are no known workarounds for this issue.
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Analysis
by VulDB Data Team • 03/05/2023
The vulnerability described in CVE-2023-23933 represents a critical access control flaw within the OpenSearch Anomaly Detection plugin that undermines the integrity of field-level security mechanisms. This issue specifically targets the application of document and field level restrictions, creating a scenario where authenticated users with the Anomaly Detector role can bypass intended access controls to obtain aggregated numerical data from restricted fields. The flaw exists in the plugin's implementation of security policies, where the system fails to properly enforce field-level restrictions when processing anomaly detection requests that involve aggregated data calculations.
The technical nature of this vulnerability stems from improper enforcement of access controls during the anomaly detection process, particularly when the system performs calculations such as averages and sums on data that should be restricted to certain users. This represents a classic case of insufficient authorization checking where the system assumes that because a user has read access to indexes containing restricted fields, they should also have access to the aggregated results of those fields. The vulnerability manifests in the plugin's processing logic where field-level restrictions are not consistently applied to aggregated numerical data, creating a data leakage channel that allows unauthorized access to sensitive information. This type of flaw falls under the CWE category of insufficient authorization checking, specifically CWE-285, which deals with improper authorization in access control systems.
The operational impact of this vulnerability is significant for organizations relying on OpenSearch for anomaly detection while maintaining strict data access controls. Attackers who have gained access to the Anomaly Detector role can potentially extract aggregated information that would normally be protected, leading to information disclosure and potential data exfiltration. The vulnerability affects authenticated users who already possess read access to indexes containing restricted fields, meaning that the attack vector involves users who have legitimate access to the system but can exploit the flaw to gain access to additional data that they should not be able to see. This creates a scenario where the existing access control policies become ineffective for aggregated data, undermining the principle of least privilege that organizations rely on for data security.
Organizations using OpenSearch with the Anomaly Detection plugin should immediately upgrade to versions 1.3.8 or 2.6.0 to address this vulnerability, as no workarounds are available for this specific flaw. The patch addresses the core issue of field-level restriction enforcement during anomaly detection processing, ensuring that aggregated numerical data calculations respect the same access controls that apply to individual field access. This vulnerability aligns with ATT&CK technique T1078.004, which covers valid accounts with elevated privileges, as it exploits legitimate user access to gain unauthorized data access through a flaw in the system's access control implementation. The issue demonstrates how even authenticated users with proper access rights can be exploited to achieve information disclosure through implementation flaws in security controls, highlighting the importance of proper access control enforcement at all levels of system processing. Organizations should conduct comprehensive security assessments to identify any potential exploitation of this vulnerability and ensure that all instances of OpenSearch are updated to mitigate the risk of unauthorized data access through aggregated anomaly detection results.