CVE-2026-18420 in OpenSearch Service
Summary
by MITRE • 08/21/2026
Improper input validation in the Time Series Visual Builder (TSVB) plugin in OpenSearch Dashboards allows an authenticated remote user to execute arbitrary code on the server via a crafted JSON payload to the metrics visualization API endpoint. This issue is a form of prototype pollution that enables remote code execution.
To remediate this issue, users should upgrade to OpenSearch Dashboards 3.8 or later.
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Analysis
by VulDB Data Team • 08/21/2026
The vulnerability identified in the Time Series Visual Builder plugin within OpenSearch Dashboards represents a critical security flaw rooted in improper input validation mechanisms. This specific weakness allows an authenticated remote user to manipulate internal object structures through crafted JSON payloads sent to the metrics visualization API endpoint. The core technical issue is classified as prototype pollution, a type of injection attack where properties are added or modified on JavaScript objects' prototypes rather than their instances. In the context of Node.js and OpenSearch Dashboards, which rely heavily on dynamic object manipulation for configuration and data processing, this flaw enables an attacker to inject malicious keys into shared prototype chains. When the application processes these polluted objects later in its execution flow, it may inadvertently execute unintended logic or load arbitrary code modules that were not originally intended by the system administrators or developers.
From a technical perspective, the exploitation of this vulnerability requires authentication, meaning the attacker must possess valid credentials to interact with the OpenSearch Dashboards interface. However, once authenticated, the barrier to achieving remote code execution is significantly lowered due to the nature of prototype pollution. By carefully constructing JSON payloads that target specific properties within the TSVB plugin's data handling routines, an adversary can overwrite critical configuration parameters or inject executable scripts into the application context. This manipulation bypasses standard security controls because the server treats these modified structures as legitimate inputs during subsequent processing steps. The result is a complete compromise of the backend server's integrity, allowing for arbitrary code execution with the privileges of the OpenSearch Dashboards process.
The operational impact of this vulnerability is severe, extending beyond mere data exposure to full system control. An attacker leveraging this flaw can execute commands on the underlying operating system, potentially leading to further lateral movement within the network infrastructure. This could involve exfiltrating sensitive data stored in or accessible by OpenSearch clusters, installing backdoors for persistent access, or using the compromised server as a pivot point for attacks against other internal services. Given that visualization tools often handle large volumes of operational and business-critical metrics, the integrity of these systems is paramount; their compromise undermines trust in monitoring capabilities and exposes organizations to significant risk during incident response scenarios where accurate data visibility is essential.
This vulnerability aligns with CWE-1325, which covers improper check for unusual or unexpected input conditions, specifically manifesting as prototype pollution leading to remote code execution. It also maps closely to MITRE ATT&CK techniques related to command and script interpretation, particularly those involving server-side JavaScript exploitation. The lack of strict schema validation on the metrics visualization API endpoint serves as the primary enabler for this attack vector, highlighting a gap in defensive coding practices where input sanitization was not adequately enforced against nested object manipulation attacks.
To remediate this critical issue, organizations must upgrade OpenSearch Dashboards to version 3.8 or later immediately. This release includes patches that enforce stricter validation rules on incoming JSON payloads and mitigate the prototype pollution vector within the Time Series Visual Builder plugin. In addition to upgrading, administrators should ensure that all plugins are updated to their latest compatible versions to address any related vulnerabilities in dependent libraries. Implementing network-level access controls to restrict API endpoint exposure further reduces the attack surface, while continuous monitoring for anomalous JSON patterns can help detect attempted exploitation activities before they result in successful code execution.