Apache NiFi 1.5.0 through 2.11.0 provide REST API methods that replace the entire contents of a Process Group using a client-supplied flow definition, covering Process Group flow replacement together with versioned flow update and rebase operations. Framework authorization for these methods was limited to read and write privileges on the Process Group itself, unlike the corresponding asynchronous update request methods, which also authorize the components encapsulated in the Process Group along with referenced Controller Services, Parameter Contexts, and Parameter Providers. As a result of the missing authorization, an authenticated user with write access to a Process Group could supply a flow definition that modifies or removes components in descendant Process Groups protected by more restrictive access policies, and could bind components to Controller Services and Parameter Contexts without authorization for those referenced components. Existing verification checks limited the impact to stopped components, and the issue applies only to deployments that use component-level authorization policies, because the framework enforces write permissions as the security boundary. Upgrading to Apache NiFi 2.12.0 is the recommended mitigation, which applies consistent reference resolution and component authorization across Process Group replacement and versioned flow update methods

Apache NiFi 1.5.0 through 2.10.0 support gzip-encoded HTTP requests for the application REST API using a Jersey encoding filter. The framework enforced a configurable maximum request size on the compressed payload rather than the decompressed output, allowing a malicious client to send crafted requests that could consume excessive amounts of memory. Upgrading to Apache NiFi 2.11.0 is the recommended mitigation, which relocates response compression to Jetty Server and disables decompression of gzip-encoded HTTP requests.