CVE-2026-33458: Kibana One Workflow SSRF Vulnerability

CVE-2026-33458 Overview

A Server-Side Request Forgery (SSRF) vulnerability has been identified in Kibana One Workflow that can lead to information disclosure. An authenticated user with workflow creation and execution privileges can bypass host allowlist restrictions in the Workflows Execution Engine, potentially exposing sensitive internal endpoints and data. This vulnerability allows attackers to make the server perform requests to unintended locations, potentially accessing internal services that should not be externally accessible.

Critical Impact

Authenticated attackers can bypass allowlist restrictions to access sensitive internal endpoints and data through SSRF, potentially compromising internal infrastructure and confidential information.

Affected Products

• Kibana One Workflow (versions prior to security update 9.3.3)

Discovery Timeline

• April 8, 2026 - CVE-2026-33458 published to NVD
• April 8, 2026 - Last updated in NVD database

Technical Details for CVE-2026-33458

Vulnerability Analysis

This SSRF vulnerability (CWE-918) exists in the Kibana One Workflow's Workflows Execution Engine. The core issue stems from insufficient validation of user-controlled URLs within workflow definitions. While Kibana implements a host allowlist mechanism to restrict outbound requests, authenticated users with workflow creation privileges can craft requests that circumvent these restrictions.

The vulnerability requires authentication and specific privileges (workflow creation and execution), which limits the attack surface. However, once exploited, the attacker can leverage the Kibana server as a proxy to access internal network resources, cloud metadata services, or other sensitive endpoints that would otherwise be unreachable from external networks.

The scope is changed (S:C in the CVSS vector), meaning successful exploitation can affect resources beyond the vulnerable component itself. While the attack complexity is high (AC:H), indicating specific conditions must be met, the potential for high confidentiality impact makes this a significant concern for organizations with sensitive internal infrastructure.

Root Cause

The root cause lies in the improper validation of user-supplied URLs within the Workflows Execution Engine. The allowlist implementation contains logic flaws that allow certain URL patterns or encoding techniques to bypass the intended restrictions. This enables authenticated users to specify destinations that should be blocked by the security controls.

Attack Vector

The attack is conducted over the network and requires an authenticated user account with workflow creation and execution privileges. The attacker crafts a malicious workflow definition containing specially constructed URLs designed to evade the host allowlist validation. When the workflow is executed, the Kibana server makes requests to these unauthorized endpoints, returning potentially sensitive data to the attacker.

Common SSRF attack patterns that may apply include:

• URL encoding manipulation to bypass allowlist pattern matching
• DNS rebinding techniques to redirect requests after validation
• Exploiting parser inconsistencies between validation and request components
• Utilizing alternative IP address representations (decimal, hexadecimal, octal)

The attacker can potentially access internal services, cloud instance metadata endpoints (e.g., 169.254.169.254), or other resources on the internal network that trust requests from the Kibana server.

Detection Methods for CVE-2026-33458

Indicators of Compromise

• Unusual outbound requests from Kibana servers to internal IP ranges or metadata endpoints
• Workflow definitions containing suspicious URLs or unusual URL encoding patterns
• Unexpected access to internal services from Kibana server IP addresses
• Anomalous workflow creation activity from specific user accounts

Detection Strategies

• Monitor Kibana audit logs for workflow creation events with unusual URL patterns
• Implement network monitoring to detect outbound requests from Kibana to internal endpoints
• Alert on requests to cloud metadata service addresses (169.254.169.254, fd00:ec2::254)
• Review workflow execution logs for failed or suspicious external requests

Monitoring Recommendations

• Enable detailed logging for the Workflows Execution Engine component
• Deploy network segmentation alerts for unexpected cross-zone traffic from Kibana hosts
• Implement egress filtering and logging at the network perimeter
• Configure SIEM rules to correlate workflow execution with unusual network activity

How to Mitigate CVE-2026-33458

Immediate Actions Required

• Update Kibana to version 9.3.3 or later which contains the security fix
• Review and audit existing workflows for potentially malicious URL patterns
• Restrict workflow creation and execution privileges to trusted users only
• Implement network-level controls to limit Kibana's outbound connectivity to only necessary destinations

Patch Information

Elastic has released a security update addressing this vulnerability. The fix is included in Kibana version 9.3.3. Organizations should update immediately by following the Elastic Security Update Notice (ESA-2026-28). The patch strengthens the host allowlist validation logic to prevent bypass attempts.

Workarounds

• Temporarily disable the Workflows feature if not critical to operations
• Implement strict network egress filtering to block access to internal networks from Kibana
• Use a web application firewall (WAF) to inspect and block suspicious workflow requests
• Apply principle of least privilege by removing workflow creation permissions from non-essential users

# Example: Network egress restriction for Kibana using iptables
# Block access to internal networks and metadata endpoints from Kibana server
iptables -A OUTPUT -m owner --uid-owner kibana -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -m owner --uid-owner kibana -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -m owner --uid-owner kibana -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -m owner --uid-owner kibana -d 169.254.169.254 -j DROP