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.
The build_public_tmp endpoint is intentionally designed as unauthenticated to handle public flows. When a POST request contains an optional data parameter, the server uses the attacker-supplied flow definition instead of data stored in the database. This definition can contain arbitrary Python code embedded in node definitions, which is then passed directly to the exec() function without any sandboxing or validation. As a result, an attacker can remotely execute arbitrary code on the server without possessing any credentials.
An unauthenticated attacker can execute arbitrary Python code in the context of the Langflow server process, leading to complete system compromise, data exfiltration, backdoor installation, or lateral movement within the internal network.
Immediately update Langflow to version 1.9.0 or later, where the vulnerability has been fixed. The patch is available in the project repository (commit 73b6612e3ef25fdae0a752d75b0fabd47328d4f0) and in the official 1.9.0 release.
Langflow in all versions prior to 1.9.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XLangflow
APPLangflow< 1.8.2
CISA KEV — detailsi
- Vendori
- Langflow
- Producti
- Langflow
- Added to KEVi
- March 25, 2026
- Remediation deadline (US Federal)i
- April 8, 2026(overdue)
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Langflow contains a code injection vulnerability that could allow building public flows without requiring authentication.
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