CVE-2026-42400: Kibana Denial of Service via Uncontrolled Resource Consumption

Technical summary

This is an uncontrolled resource consumption vulnerability (CWE-400) stemming from improper sequencing of security checks in Kibana's request handling pipeline. An authenticated attacker crafts a specially compressed payload that triggers excessive decompression and processing before the application reaches authorization enforcement. The early processing of untrusted compressed data without resource limits allows an attacker to allocate memory and CPU cycles disproportionately, exhausting server capacity. The vulnerability is network-accessible and requires only valid authentication credentials—no user interaction is needed. The CVSS 3.1 score of 6.5 (Medium) reflects that availability is severely impacted while confidentiality and integrity remain unaffected.

Business impact

Kibana outages directly impact security operations, observability, and incident response. When a Kibana instance becomes unresponsive or crashes due to this vulnerability, analysts lose real-time access to logs, metrics, and security events. For organizations using Kibana as their primary analytics platform, even a brief denial of service can blind SOCs to ongoing threats, delay incident detection, and complicate forensics. An authenticated attacker—whether a compromised internal account or a malicious insider—can weaponize this to disrupt operations precisely when visibility matters most. Recovery requires manual restart, and in multi-tenant or clustered environments, the blast radius could extend across multiple users or systems.

Affected systems

All versions of Elastic Kibana are potentially affected by this vulnerability, though the specific affected version range should be confirmed against Elastic's official security advisory. Organizations running Kibana as part of their Elastic Stack deployment are in scope. The vulnerability requires valid Kibana authentication credentials, so public internet-facing instances without proper access controls or those with weak credential management face elevated risk.

Exploitability

This vulnerability is moderately exploitable. It requires valid authentication credentials, which raises the bar compared to unauthenticated DoS attacks but is still achievable for attackers who have obtained legitimate user accounts or compromised internal users. Crafting the malicious compressed payload requires moderate technical knowledge of Kibana's request format and compression handling, but the attack itself is straightforward to execute once understood. No complex exploitation techniques or race conditions are involved. The lack of a public exploit or KEV listing suggests active exploitation is not yet widespread, but the simplicity of the attack means the threat level could escalate rapidly if proof-of-concept code is published.

Remediation

Organizations should prioritize patching Kibana to a version that implements proper resource limits and moves authorization checks before request processing and decompression. Consult Elastic's official security advisory for the specific patched version applicable to your deployed version. As an interim control, network-level rate limiting on Kibana endpoints can reduce the window for resource exhaustion attacks. Restricting Kibana access to trusted internal networks and enforcing strong authentication (MFA where available) reduces the likelihood that an attacker can obtain valid credentials needed to exploit this vulnerability.

Patch guidance

Check Elastic's official security advisories and release notes to identify which Kibana version addresses this vulnerability. Patch testing should validate that request processing handles compression safely and that authorization checks occur before resource-intensive operations. Apply patches in a test environment first to ensure compatibility with your Kibana configuration, custom plugins, and connected data sources. Coordinate patching during a maintenance window to avoid disrupting ongoing monitoring, or perform rolling updates in clustered Kibana deployments to maintain availability. Verify patch installation by checking Kibana's version reporting endpoint after upgrade.

Detection guidance

Monitor Kibana logs for repeated error messages or warnings related to request processing failures, decompression errors, or resource exhaustion events. Watch for sudden spikes in memory usage or CPU consumption that correlate with specific API requests or user activity. Implement alerting on Kibana node crashes or unresponsiveness, as these may indicate ongoing exploitation. Network-level detection can flag unusual compression patterns or oversized request payloads sent to Kibana endpoints from authenticated users. Consider baselines for normal resource consumption patterns within your environment and alert on anomalies that suggest resource-exhaustion attacks.

Why prioritize this

Although rated CVSS 6.5 (Medium), this vulnerability warrants prompt attention because it directly impacts operational security. Unlike vulnerabilities that affect data confidentiality or integrity indirectly, this DoS attack immediately disables a critical security tool. The authentication requirement does moderate risk compared to unauthenticated DoS attacks, but organizations relying on Kibana for real-time threat detection should treat this as a higher operational priority. The lack of KEV listing indicates this is not yet a widespread, targeted attack vector, providing a window to patch before threat actors adapt. In environments with strong access controls and limited internal user bases, risk is lower; in organizations with more permissive credential sharing or compromised user accounts, risk is higher.

Risk score, explained

The CVSS 6.5 score reflects a Medium severity rating driven by high availability impact (the attack causes crashes or unresponsiveness) but no direct impact to confidentiality or integrity. The attack requires network access and valid authentication credentials, which are limiting factors compared to unauthenticated network attacks. The low complexity of crafting and executing the attack once authenticated keeps the score from being lower. Organizations with strict access controls and multi-factor authentication on Kibana should view this as lower risk; those with weaker credential hygiene should view it as closer to High priority operationally, even if the CVSS score remains Medium.

Frequently asked questions