CVE-2026-25903 is a missing authorization vulnerability (CWE-862) in Apache NiFi versions 1.1.0 through 2.7.2. Apache NiFi uses a Restricted annotation to mark extension components that require elevated privileges to be added to flow configurations. However, while the framework enforces these privileges when adding such components, it fails to enforce them when updating configuration properties of these components once added. This means that a user with lower privileges than required to add the component can still modify its configuration properties, potentially altering the behavior of the data flows or introducing malicious configurations. The vulnerability arises because the authorization framework does not check the Restricted status during property updates, only during component addition. This flaw can lead to unauthorized changes that compromise the confidentiality, integrity, and availability of data flows managed by NiFi. The vulnerability requires the attacker to have some level of authenticated access and user interaction but does not require full administrative privileges. The recommended mitigation is to upgrade to Apache NiFi version 2.8.0, where this authorization check has been corrected. Organizations that implement strict authorization boundaries for Restricted components are not vulnerable, as the write permissions act as a security boundary preventing unauthorized changes.

For European organizations, this vulnerability poses a significant risk especially for those relying on Apache NiFi for critical data flow management, including sectors like finance, healthcare, telecommunications, and public services. Unauthorized configuration changes could lead to data leakage, manipulation of data processing pipelines, or disruption of services, impacting confidentiality, integrity, and availability. Attackers exploiting this flaw could alter data routing, inject malicious data, or disable security controls embedded in NiFi flows. Given NiFi’s role in automating and securing data flows, exploitation could cascade into broader operational disruptions or compliance violations under regulations such as GDPR. The vulnerability’s high CVSS score (8.7) reflects the serious nature of these impacts. Organizations with multi-tenant environments or complex authorization models are particularly at risk if they have not segmented permissions properly. The lack of known exploits in the wild currently reduces immediate risk but does not diminish the urgency of remediation due to the potential for impactful misuse.

1. Upgrade all Apache NiFi instances to version 2.8.0 or later, where the authorization checks for Restricted components during property updates are enforced. 2. Review and enforce strict authorization policies differentiating between users who can add Restricted components and those who can modify their properties. 3. Implement role-based access control (RBAC) with least privilege principles, ensuring that only trusted administrators can modify sensitive configuration properties. 4. Audit existing NiFi flows for Restricted components and verify that only authorized personnel have modification rights. 5. Monitor NiFi logs for unusual configuration changes or access patterns indicative of unauthorized activity. 6. Use network segmentation and firewall rules to limit access to NiFi management interfaces to trusted networks and users. 7. Regularly review and update security policies and user permissions in line with organizational changes. 8. Consider implementing multi-factor authentication (MFA) for NiFi access to reduce the risk of compromised credentials being used to exploit this vulnerability.