CVE-2026-26935 Overview
CVE-2026-26935 is an Improper Input Validation vulnerability (CWE-20) affecting the internal Content Connectors search endpoint in Kibana. This flaw allows authenticated attackers to manipulate input data in a way that causes a Denial of Service condition, disrupting the availability of Kibana services for legitimate users.
Critical Impact
Authenticated users can exploit improper input validation in Kibana's Content Connectors search endpoint to cause service unavailability, potentially disrupting security monitoring and analytics operations.
Affected Products
- Kibana versions prior to 8.19.12
- Kibana versions prior to 9.2.6
- Kibana versions prior to 9.3.1
Discovery Timeline
- February 26, 2026 - CVE-2026-26935 published to NVD
- February 26, 2026 - Last updated in NVD database
Technical Details for CVE-2026-26935
Vulnerability Analysis
This vulnerability stems from inadequate input validation within Kibana's internal Content Connectors search endpoint. When the endpoint processes specially crafted input data, it fails to properly validate or sanitize the input parameters, leading to resource exhaustion or application crash conditions.
The flaw allows an authenticated attacker with network access to send malicious requests that exploit the input validation weakness. Since the vulnerability requires low-privilege authentication but no user interaction, it presents a significant risk to organizations relying on Kibana for security monitoring and log analysis. The impact is limited to availability—there is no unauthorized data access or integrity compromise.
Root Cause
The root cause is Improper Input Validation (CWE-20) in the Content Connectors search endpoint. The application fails to properly validate, filter, or sanitize input data before processing it, allowing attackers to supply malformed or excessive input that triggers resource exhaustion or crashes the service.
Attack Vector
The attack is network-based and requires low-privilege authentication to the Kibana instance. An attacker can exploit this vulnerability by sending specially crafted requests to the internal Content Connectors search endpoint. The attack does not require user interaction and can be executed remotely against any accessible Kibana deployment.
The vulnerability follows the Input Data Manipulation attack pattern (CAPEC-153), where an attacker deliberately provides malformed or unexpected input to trigger unintended behavior—in this case, a Denial of Service condition that impacts the availability of the Kibana service.
Detection Methods for CVE-2026-26935
Indicators of Compromise
- Unusual volume of requests to the Content Connectors search endpoint from a single user or source
- Kibana service crashes or restarts occurring in correlation with specific API requests
- Error logs indicating input validation failures or resource exhaustion in the Content Connectors module
- Authenticated user accounts making abnormal query patterns to internal search endpoints
Detection Strategies
- Monitor Kibana access logs for anomalous request patterns targeting the Content Connectors search endpoint
- Implement rate limiting and anomaly detection for authenticated API requests
- Configure alerts for Kibana service instability, unexpected restarts, or memory exhaustion events
- Review authentication logs for suspicious activity from accounts accessing internal endpoints
Monitoring Recommendations
- Enable detailed logging for the Content Connectors module to capture request parameters and error conditions
- Deploy application performance monitoring to detect resource exhaustion patterns before complete service failure
- Implement network-level monitoring to identify unusual traffic patterns to Kibana endpoints
- Configure health check alerts to immediately notify administrators of Kibana service degradation
How to Mitigate CVE-2026-26935
Immediate Actions Required
- Update Kibana to the patched versions: 8.19.12, 9.2.6, or 9.3.1 depending on your deployment branch
- Review access controls to restrict which users can access internal Content Connectors endpoints
- Implement network segmentation to limit exposure of Kibana services to trusted networks only
- Enable rate limiting on Kibana API endpoints to reduce the impact of potential exploitation attempts
Patch Information
Elastic has released security patches addressing this vulnerability in Kibana versions 8.19.12, 9.2.6, and 9.3.1. Organizations should upgrade to the appropriate patched version based on their current deployment. Detailed patch information is available in the Elastic Security Update ESA-2026-13.
Workarounds
- Restrict network access to Kibana services using firewall rules or security groups to limit exposure to trusted networks
- Implement Web Application Firewall (WAF) rules to filter potentially malicious requests to Content Connectors endpoints
- Review and minimize the number of user accounts with access to internal Kibana endpoints
- Consider temporarily disabling the Content Connectors feature if not actively required while awaiting patching
# Example: Restrict Kibana access via firewall (adjust IPs for your environment)
# Allow access only from trusted management network
iptables -A INPUT -p tcp --dport 5601 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 5601 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
