CVE-2026-25903: Apache NiFi Privilege Escalation Flaw

CVE-2026-25903 Overview

Apache NiFi versions 1.1.0 through 2.7.2 contain a missing authorization vulnerability when updating configuration properties on extension components that have specific Required Permissions based on the Restricted annotation. The Restricted annotation indicates additional privileges required to add the annotated component to the flow configuration, but the framework authorization did not check restricted status when updating a component that was previously added. This missing authorization check allows a less privileged user to make property configuration changes to restricted components after a more privileged user has added them to the flow configuration.

Critical Impact

Organizations using Apache NiFi with multi-level authorization for Restricted components may be vulnerable to privilege escalation attacks where low-privileged users can modify sensitive configuration properties on restricted extension components, potentially leading to data exfiltration or system compromise.

Affected Products

• Apache NiFi 1.1.0 through 2.7.2

Discovery Timeline

• 2026-02-17 - CVE CVE-2026-25903 published to NVD
• 2026-02-18 - Last updated in NVD database

Technical Details for CVE-2026-25903

Vulnerability Analysis

This vulnerability is classified as CWE-862 (Missing Authorization). The core issue resides in Apache NiFi's framework authorization mechanism, which fails to properly validate restricted component status during configuration update operations. When a restricted extension component is added to a NiFi flow, the framework correctly enforces the elevated privileges required by the Restricted annotation. However, subsequent property configuration changes bypass this authorization check entirely.

The vulnerability specifically affects environments where different authorization levels are implemented for Restricted components. In such deployments, a user with lower privileges can modify the configuration of restricted components that were added by users with higher privileges. This creates a security gap where the initial access control is enforced but ongoing modifications are not properly restricted.

Apache NiFi installations that do not implement different levels of authorization for Restricted components are not subject to this vulnerability because the framework enforces write permissions as the security boundary in those configurations.

Root Cause

The root cause is a missing authorization check in the Apache NiFi framework when processing configuration update requests for extension components marked with the Restricted annotation. While the framework correctly validates required permissions when initially adding restricted components to the flow configuration, it fails to re-validate restricted status during property modification operations. This creates an authorization bypass where the access control model is inconsistently applied between create and update operations.

Attack Vector

The attack vector is network-based and requires authenticated access to the Apache NiFi web interface. An attacker with low-privilege credentials must wait for a more privileged user to add a restricted component to the flow configuration. Once the restricted component exists in the flow, the low-privileged user can send update requests to modify the component's configuration properties.

The attack scenario involves:

1. A privileged administrator adds a restricted extension component to the NiFi flow (e.g., a component with file system access or database connectivity)
2. A low-privileged user, who would normally be blocked from adding such components, sends a configuration update request
3. The framework processes the update without checking the restricted status, allowing unauthorized property modifications
4. The attacker modifies sensitive configuration properties such as connection strings, file paths, or execution parameters

For detailed technical information, see the Apache Mailing List Discussion and the OpenWall OSS-Security Message.

Detection Methods for CVE-2026-25903

Indicators of Compromise

• Unexpected configuration changes to restricted extension components in NiFi flow configurations
• Audit log entries showing configuration modifications by users without appropriate restricted component permissions
• Property changes to sensitive components such as database connectors, file processors, or script executors made by non-administrative accounts

Detection Strategies

• Enable comprehensive audit logging in Apache NiFi to track all configuration modification events
• Monitor for configuration update requests targeting components with the Restricted annotation from users without elevated privileges
• Implement alerting on any modifications to sensitive processor properties by users outside of approved administrator groups
• Review NiFi's nifi-user.log for unauthorized configuration change attempts

Monitoring Recommendations

• Configure SIEM integration with Apache NiFi to correlate user authorization levels with component modification events
• Establish baselines for normal configuration change patterns and alert on deviations
• Implement real-time monitoring of flow configuration changes with user attribution
• Regularly audit the list of users with access to the NiFi interface and their assigned permissions

How to Mitigate CVE-2026-25903

Immediate Actions Required

• Upgrade to Apache NiFi 2.8.0 immediately as the recommended mitigation
• Audit existing NiFi flow configurations to identify any restricted components that may have been modified by unauthorized users
• Review user access permissions and restrict NiFi web interface access to only necessary personnel
• Implement network segmentation to limit access to the NiFi administrative interface

Patch Information

The recommended mitigation is upgrading to Apache NiFi 2.8.0, which addresses the missing authorization check for restricted component configuration updates. Organizations should plan and execute the upgrade as soon as possible, following the official Apache NiFi upgrade documentation. Review the Apache Mailing List Discussion for additional patch details and guidance.

Workarounds

• If upgrading is not immediately possible, restrict NiFi web interface access to only trusted administrative users through network-level controls
• Implement a unified authorization model where all users have the same level of restricted component access, eliminating the differential privilege levels that enable exploitation
• Enable comprehensive audit logging and implement manual review processes for all configuration changes pending upgrade
• Consider placing NiFi behind an additional authentication layer to limit exposure

# Configuration example - Restrict NiFi web interface access via firewall
# Allow only trusted admin IPs to access NiFi web interface (default port 8443)
iptables -A INPUT -p tcp --dport 8443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8443 -j DROP

# Enable audit logging in nifi.properties
# nifi.security.user.login.identity.provider=ldap-provider
# nifi.administrative.yield.duration=30 sec