CVE-2026-81941 in Langflow OSS
Summary
by MITRE • 09/11/2026
IBM Langflow OSS 1.0.0 through 1.11.5 allows an authenticated non-administrative user could execute arbitrary operating system commands on the server at the privilege level of the application process by constructing a flow with an MCP Tools component configured to use a local stdio subprocess transport. This bypasses both the LANGFLOW_CUSTOM_COMPONENT_ADMIN_ONLY and LANGFLOW_BLOCK_CODE_INTERPRETER_COMPONENTS server-side controls intended to prevent exactly this class of access. Successful exploitation could lead to arbitrary command execution, sensitive data exposure (including credentials from the process environment), file system modification, and lateral movement to services reachable from the server.
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Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified in IBM Langflow versions 1.0.0 through 1.11.5 represents a critical privilege escalation flaw that allows authenticated non-administrative users to achieve arbitrary command execution on the underlying host system. This issue stems specifically from the implementation of the MCP Tools component, which supports various transport mechanisms for interacting with external tools and services. When an attacker configures this component to utilize a local stdio subprocess transport, they can effectively spawn operating system processes directly within the context of the Langflow application server. The severity of this flaw is compounded by its ability to bypass established security controls designed to restrict such capabilities. Specifically, the vulnerability circumvents both the LANGFLOW_CUSTOM_COMPONENT_ADMIN_ONLY and LANGFLOW_BLOCK_CODE_INTERPRETER_COMPONENTS environment variables or configuration settings that are intended to prevent non-admin users from executing code or running custom components with elevated privileges.
From a technical perspective, this flaw is classified as an OS Command Injection vulnerability, aligning closely with CWE-78 in the Common Weakness Enumeration standard. The root cause lies in insufficient validation and access control checks when instantiating subprocesses via the stdio transport mechanism. Instead of restricting such operations to administrative users or sandboxed environments, the application allows any authenticated user to define a flow that triggers system-level commands. This architectural oversight means that the security boundary between the web application layer and the operating system is effectively neutralized for non-admin accounts. The attacker does not need to exploit complex buffer overflows or memory corruption issues; rather, they leverage legitimate functionality in an unintended manner to execute arbitrary shell commands with the same permissions as the Langflow process itself.
The operational impact of this vulnerability is severe and multifaceted. Successful exploitation grants the attacker full control over the server at the privilege level of the application process. This typically means that if the service runs under a dedicated user account, the attacker gains access to all files readable by that user, including sensitive configuration files, database connection strings, and API keys stored in environment variables or local storage. Beyond data exfiltration, the ability to execute arbitrary commands enables file system modifications, such as planting backdoors, modifying application logic, or deleting critical logs to cover tracks. Furthermore, this level of access facilitates lateral movement within the network infrastructure. The attacker can use the compromised server as a pivot point to scan internal networks, attack other services reachable from the host, and potentially escalate privileges further if local privilege escalation vulnerabilities exist on the operating system.
This incident is also relevant to the MITRE ATT&CK framework, particularly under techniques involving Command and Scripting Interpreter execution (T1059) and System Network Connections Discovery (T1046). The attacker leverages standard OS utilities to execute commands and potentially probe for other vulnerable systems on the local network. To mitigate this risk, organizations running IBM Langflow must immediately upgrade to a patched version where these access controls are properly enforced or where the stdio transport is restricted exclusively to administrative users with verified identities. In environments where upgrading is not immediately feasible, administrators should ensure that LANGFLOW_BLOCK_CODE_INTERPRETER_COMPONENTS and LANGFLOW_CUSTOM_COMPONENT_ADMIN_ONLY are strictly enabled and tested for efficacy against non-admin accounts. Additionally, deploying Langflow within a containerized environment with strict resource limits and network policies can help contain the blast radius of such an exploitation attempt by restricting outbound connections and limiting file system access to only necessary directories.