CVE-2026-82561: Apache NiFi Privilege Escalation Vulnerability

CVE-2026-82561 Overview

CVE-2026-82561 is a missing authorization vulnerability [CWE-862] affecting Apache NiFi versions 1.5.0 through 2.11.0. The flaw resides in REST API methods that replace the entire contents of a Process Group using a client-supplied flow definition. These methods include Process Group flow replacement, versioned flow update, and rebase operations. Framework authorization was limited to read and write privileges on the parent Process Group. It did not authorize the encapsulated components, referenced Controller Services, Parameter Contexts, or Parameter Providers. An authenticated user with write access can therefore modify descendant components protected by stricter policies.

Critical Impact
An authenticated user with write access to a Process Group can modify or remove components in descendant Process Groups protected by more restrictive access policies, and can bind components to Controller Services and Parameter Contexts without authorization for those referenced components.

Affected Products

Apache NiFi 1.5.0 through 1.x releases
Apache NiFi 2.0.0 through 2.11.0
Deployments configured with component-level authorization policies

Discovery Timeline

2026-09-16 - CVE CVE-2026-82561 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-82561

Vulnerability Analysis

Apache NiFi exposes REST API endpoints that let clients supply a complete flow definition to replace the contents of a Process Group. These endpoints handle Process Group flow replacement, versioned flow update, and rebase operations. The framework performs authorization checks that validate only read and write privileges on the target Process Group. It does not walk the supplied flow definition to authorize each encapsulated component, referenced Controller Service, Parameter Context, or Parameter Provider.

The corresponding asynchronous update request methods perform the deeper authorization walk. This inconsistency creates the security gap. An authenticated user with write permission on a parent Process Group can submit a crafted flow definition that alters or deletes components in descendant Process Groups. The user can also bind components to Controller Services and Parameter Contexts without holding permissions on those referenced components.

Root Cause

The root cause is a missing authorization check [CWE-862] in the synchronous flow replacement code paths. Framework authorization treated write access on the Process Group as the security boundary. It did not resolve and authorize the referenced components inside the submitted flow definition.

Attack Vector

Exploitation requires an authenticated account with write access to a Process Group in a NiFi deployment that uses component-level authorization policies. The attacker submits a flow definition through the affected REST API methods that references or removes components in descendant Process Groups. Existing verification checks limit the impact to stopped components. Deployments that do not use component-level authorization policies are not affected because the framework already enforces write permissions as the security boundary.

The vulnerability is described in prose only; no verified public proof-of-concept code is available. See the Apache Mailing List Discussion and the Openwall OSS-Security Update for the official advisory content.

Detection Methods for CVE-2026-82561

Indicators of Compromise

Unexpected modification or removal of components within descendant Process Groups by users lacking direct permissions on those components
New or modified bindings between components and Controller Services or Parameter Contexts that reference resources outside the acting user's authorized scope
REST API calls to Process Group flow replacement, versioned flow update, or rebase endpoints originating from lower-privileged accounts

Detection Strategies

Enable and review NiFi audit logs for updateFlow, replaceProcessGroup, and version control update events, correlating the acting user with the target and descendant Process Group policies
Compare snapshots of flow definitions before and after replacement operations to identify unauthorized structural changes
Alert on REST API POST or PUT requests to /nifi-api/process-groups/{id}/flow-contents and versioned flow endpoints from non-administrative accounts

Monitoring Recommendations

Forward NiFi framework and user audit logs to a centralized logging platform for retention and correlation
Baseline normal flow-modification activity per user and role, then alert on deviations targeting descendant Process Groups
Monitor Controller Service and Parameter Context binding changes for reference targets outside the acting user's authorization scope

How to Mitigate CVE-2026-82561

Immediate Actions Required

Upgrade Apache NiFi to version 2.12.0, which applies consistent reference resolution and component authorization across Process Group replacement and versioned flow update methods
Inventory all NiFi deployments to identify instances running versions 1.5.0 through 2.11.0 that use component-level authorization policies
Review current Process Group write permissions and revoke access for accounts that do not require flow modification capabilities

Patch Information

Upgrade to Apache NiFi 2.12.0. This release resolves the inconsistency by applying the same reference resolution and component authorization logic used by the asynchronous update request methods to the synchronous Process Group replacement, versioned flow update, and rebase operations. Refer to the Apache Mailing List Discussion for the vendor announcement.

Workarounds

Restrict write access on parent Process Groups so only trusted administrators can invoke flow replacement or versioned flow update operations
Audit and tighten component-level authorization policies to ensure descendant components are owned by roles distinct from users holding parent-level write access
Where feasible, disable or block REST API access to Process Group replacement and versioned flow update endpoints for non-administrative accounts at a reverse proxy or API gateway

bash

# Configuration example: verify installed NiFi version and plan upgrade
./bin/nifi.sh status
cat ./conf/nifi.properties | grep -i version
# Upgrade to Apache NiFi 2.12.0 following the official migration guide