CVE-2026-51886 langflow-ai CVE debrief

Who should care

Langflow users and administrators, security teams responsible for Python applications, and DevOps teams managing Langflow deployments should assess exposure and apply patches. They should also review compensating controls for exposed systems while remediation is scheduled and verified.

Why it matters

Authenticated Remote Code Execution (RCE) vulnerability in Langflow's validate_code function allows authenticated users to execute arbitrary code on the server, potentially resulting in full system compromise.

• Potential full system compromise for Langflow servers
• Code execution with elevated privileges for authenticated users
• Possible lateral movement within the network
• Data tampering and unauthorized access to sensitive information

Technical summary

The validate_code function in Langflow executes user-supplied code using Python's exec() function, allowing authenticated users to execute arbitrary code on the server. The function attempts to restrict execution to function definitions but fails to account for decorators, which are evaluated at definition time. This allows any authenticated user to execute arbitrary code on the server, resulting in a full system compromise. The vulnerability is located in src/lfx/src/lfx/custom/validate.py, exposed via src/backend/base/langflow/api/v1/validate.py.

Defensive priority

High priority for Langflow users and administrators to assess exposure and apply patches

Recommended defensive actions

• Assess exposure by reviewing Langflow deployment and user authentication configurations
• Verify if Langflow version is 1.10.1 or later, and apply patches if necessary
• Restrict access to the /api/v1/validate/code endpoint for authenticated users
• Monitor Langflow server logs for suspicious activity
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The vulnerability is located in src/lfx/src/lfx/custom/validate.py, exposed via src/backend/base/langflow/api/v1/validate.py. The validate_code function parses user input using ast and executes it using Python's exec() function. The function attempts to restrict execution to function definitions but fails to account for decorators, which are evaluated at definition time.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.