What happened
Prior to Langflow 1.9.1, unauthenticated users can upload unlimited data to the server via the file upload endpoint with no size or rate limits. This can exhaust disk space on the server, rendering Langflow unusable for all users indefinitely. CVSS 9.3 Critical, published 2026-06-23.
Why it matters
A no-auth DoS against a production AI workflow platform disrupts all running agent pipelines and AI deployments on the instance. Attackers can trivially take down shared Langflow infrastructure used by multiple teams, causing cascading failures in automated AI processes that depend on Langflow flows.
Attack vector
Unauthenticated repeated file upload requests to Langflow's upload endpoint with large files; no server-side size limit or authentication check exhausts disk space
Affected systems
Langflow < 1.9.1
Mitigation
Upgrade to Langflow 1.9.1. PR fix: https://github.com/langflow-ai/langflow/pull/12831