U.S. CISA adds a Langflow flaw to its Known Exploited Vulnerabilities catalog

Langflow, an open-source visual framework for building LLM and agentic AI applications, contains a missing authentication flaw (CWE-306) in its /api/v1/validate/code endpoint. A remote attacker with network reachability to the endpoint can send crafted HTTP requests without any credentials, causing arbitrary code execution on the server. Successful exploitation yields code execution under the application's privileges, enabling data theft, backdoor installation, and, per CISA, ransomware deployment. Any running Langflow instance is affected; the tool is typically self-hosted by development teams building AI workflows, so real-world exposure depends on whether each instance is reachable from untrusted networks. Exploitation is confirmed in the wild: the flaw was added to CISA's KEV catalog on 2025-05-05 with known ransomware use, EPSS assigns a 100% probability of exploitation within 30 days (100th percentile), and a public PoC is available.

Do: Upgrade Langflow to the latest patched release identified in the vendor's advisory; federal agencies must apply mitigations per vendor instructions under BOD 22-01 or discontinue use if mitigations are unavailable. Until patched, restrict network access to the /api/v1/validate/code endpoint via reverse-proxy authentication, firewall rules, or VPN placement, and avoid exposing Langflow directly to the internet. Because ransomware use is confirmed, review access and process-execution logs for signs of prior compromise.

CVE-2026-33017 is an unauthenticated remote code execution flaw in Langflow, an open-source tool for building and deploying AI-powered agents and workflows. The POST /api/v1/build_public_tmp/{flow_id}/flow endpoint, which by design requires no authentication for building public flows, accepts an optional data parameter; when present, attacker-controlled flow data — including arbitrary Python code embedded in node definitions — is used instead of the flow stored in the database and passed to exec() with no sandboxing. An attacker who can reach this endpoint on an affected instance can therefore execute arbitrary Python code without any credentials, typically yielding full compromise of the underlying server. All Langflow versions prior to 1.9.0 are affected; the issue was fixed in 1.9.0 and is distinct from CVE-2025-3248, which only added authentication to the /api/v1/validate/code endpoint. The flaw was added to CISA's KEV catalog on 2026-03-25 (confirming exploitation in the wild), carries a 96.2% EPSS probability of exploitation within 30 days, and related reporting describes Langflow RCE attacks, including ransomware activity targeting AI model files.

Do: Upgrade all Langflow deployments to 1.9.0 or later. If immediate patching is not possible, keep Langflow off direct internet exposure (place it behind an authenticating reverse proxy or firewall) and review logs for unauthenticated POST requests to /api/v1/build_public_tmp/{flow_id}/flow that include a data parameter, which would indicate exploitation attempts. As a KEV entry, federal agencies must apply mitigations per vendor guidance and BOD 22-01, or discontinue use of the product if mitigations are unavailable.