Langflow RCE via build_public_tmp UE before 1.9
CVE-2026-33017 Published on March 20, 2026
Langflow has Unauthenticated Remote Code Execution via Public Flow Build Endpoint
Langflow is a tool for building and deploying AI-powered agents and workflows. In versions prior to 1.9.0, the POST /api/v1/build_public_tmp/{flow_id}/flow endpoint allows building public flows without requiring authentication. When the optional data parameter is supplied, the endpoint uses attacker-controlled flow data (containing arbitrary Python code in node definitions) instead of the stored flow data from the database. This code is passed to exec() with zero sandboxing, resulting in unauthenticated remote code execution. This is distinct from CVE-2025-3248, which fixed /api/v1/validate/code by adding authentication. The build_public_tmp endpoint is designed to be unauthenticated (for public flows) but incorrectly accepts attacker-supplied flow data containing arbitrary executable code. This issue has been fixed in version 1.9.0.
Known Exploited Vulnerability
This Langflow Code Injection Vulnerability is part of CISA's list of Known Exploited Vulnerabilities. Langflow contains a code injection vulnerability that could allow building public flows without requiring authentication.
The following remediation steps are recommended / required by April 8, 2026: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Weakness Types
What is a Code Injection Vulnerability?
The software constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
CVE-2026-33017 has been classified to as a Code Injection vulnerability or weakness.
What is an Eval Injection Vulnerability?
The software receives input from an upstream component, but it does not neutralize or incorrectly neutralizes code syntax before using the input in a dynamic evaluation call (e.g. "eval"). This may allow an attacker to execute arbitrary code, or at least modify what code can be executed.
CVE-2026-33017 has been classified to as an Eval Injection vulnerability or weakness.
Missing Authentication for Critical Function
The software does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
Affected Versions
langflow-ai langflow Version < 1.9.0 is affected by CVE-2026-33017Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.