CVE-2026-26940: 
Kibana vulnerability analysis and mitigation

CVE-2026-26940 is a Denial of Service vulnerability in the Timelion visualization plugin of Kibana, caused by improper validation of specified quantity in input (CWE-1284). An authenticated user can send a specially crafted Timelion expression that overwrites internal series data properties with an excessively large quantity value, triggering excessive memory allocation (CAPEC-130). Affected versions include Kibana 8.0.0 through 8.19.12, 9.0.0 through 9.2.6, and 9.3.0 through 9.3.1. The vulnerability was disclosed on March 19, 2026, and carries a CVSS v3.1 base score of 6.5 (Medium) (Red Hat Advisory, Elastic Security Update).

The root cause is CWE-1284 (Improper Validation of Specified Quantity in Input) within Kibana's Timelion visualization plugin. When processing Timelion expressions, the plugin fails to validate or bound quantity values used in series data properties, allowing an attacker to supply an excessively large value that causes the application to attempt excessive memory allocation (CAPEC-130: Excessive Allocation). Exploitation requires only low-privilege authenticated access over the network, with no user interaction needed. No public proof-of-concept code has been identified at this time (Red Hat Bugzilla, Elastic Security Update).

Successful exploitation results in a high availability impact — the Kibana service can experience severe resource exhaustion or a complete denial of service due to excessive memory allocation triggered by the malicious Timelion expression. There is no confidentiality or integrity impact; the vulnerability is limited to disrupting service availability. Organizations relying on Kibana for log analysis, monitoring, or security operations dashboards would lose visibility during an attack (Red Hat Advisory, Elastic Security Update).

There is no evidence of public proof-of-concept exploit code or active in-the-wild exploitation at this time. The EPSS score is approximately 0.044%, indicating a low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Detection is available via Nessus plugin ID 303586 (Tenable, Red Hat Advisory).

1. Authentication: Obtain valid Kibana credentials with at least low-privilege access to a vulnerable instance (Kibana 8.0.0–8.19.12, 9.0.0–9.2.6, or 9.3.0–9.3.1).
2. Access Timelion: Navigate to the Timelion visualization plugin within the Kibana interface.
3. Craft malicious expression: Construct a Timelion expression that sets an internal series data property (such as a quantity or size parameter) to an excessively large numeric value, bypassing input validation.
4. Submit expression: Submit the crafted expression to the Kibana backend, causing the server to attempt allocation of an excessive amount of memory.
5. Trigger DoS: The Kibana process exhausts available memory resources, resulting in service degradation or a complete crash, denying access to legitimate users (Red Hat Bugzilla, Elastic Security Update).

• Logs: Kibana server logs showing repeated or unusual Timelion expression submissions from a single authenticated user; out-of-memory (OOM) errors or heap allocation failures in Kibana application logs.
• Process/Resource: Sudden spike in Kibana process memory consumption leading to service unresponsiveness or crash; Node.js heap exhaustion errors in Kibana stdout/stderr.
• Network: Repeated API requests to Timelion-related endpoints (e.g., /api/timelion/run) from a single source IP, particularly with large or unusual payload sizes.
• Application: Kibana service restarts or health check failures coinciding with Timelion expression submissions (Red Hat Bugzilla).

Elastic has released patched versions: 8.19.13, 9.2.7, and 9.3.2. Organizations should upgrade to the appropriate fixed version based on their deployment branch as the primary remediation. As a workaround, access to the Timelion visualization plugin should be restricted to trusted, authorized users only, and Kibana resource utilization and logs should be monitored for suspicious Timelion expressions or unusual memory allocation patterns (Elastic Security Update, Red Hat Advisory).

Elastic published a security update (ESA-2026-20) covering this and related vulnerabilities in Kibana versions 8.19.13, 9.2.7, and 9.3.2. Red Hat tracked the issue via Bugzilla (Bug 2449139) and issued a corresponding security advisory. No notable independent researcher commentary or significant social media discussion has been identified beyond standard vulnerability aggregator coverage (Elastic Security Update, Red Hat Advisory).