CVE Exploit Alert: CVE-2026-33017 | CRITICAL | CVSS 9.3 | Langflow Langflow

CRITICAL

Alert Date: 2026-05-02

Severity Overview

Summary

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.

What the Attack Looks Like

How it works: Attacker-controlled data is interpreted as executable code by the application’s runtime, enabling arbitrary code execution within the application’s security context.

Analyst Takeaway

The attack is launched over the network (remotely exploitable without physical access) and no authentication is required. This vulnerability is already in CISA KEV, which means exploitation has been confirmed in the wild — treat this as active risk, not theoretical exposure. The CVSS score places this in critical territory, so internet-facing systems and high-value assets should be prioritized for immediate remediation or compensating controls. In parallel with patching, defenders should review external exposure, hunt for signs of exploitation, and validate whether compensating controls are in place for vulnerable assets.

Detection Guidance

• CWE-94 — Code Injection
  • Application logs: Look for code syntax in user-controlled fields — language-specific markers such as PHP tags (<?php), Python exec( / eval(, JavaScript Function(, template injection markers (e.g., {{7*7}}, ${7*7}).
  • Process execution: Code injection frequently results in the application process spawning unexpected child processes. Hunt for interpreter processes (python, php, node, ruby) spawned from unexpected parents.
  • Template injection: Server-side template injection often leaves arithmetic test results in response bodies during reconnaissance. WAF logs that capture response content can reveal this.

Recommended Actions

Immediate (0–24 Hours)

• Inventory: Identify all systems running Langflow Langflow. Include production, staging, dev, and cloud environments — untracked instances are the most likely to remain unpatched.
• Validate internet-facing exposure: Determine which of the affected systems are reachable from the public internet. Prioritize these for immediate remediation or compensating controls.
• Apply compensating controls now: For systems that cannot be patched immediately, implement temporary mitigations: restrict access via firewall rules or ACLs, add WAF rules if applicable, disable or isolate the vulnerable component if feasible without breaking critical operations.

Remediation

• Apply the vendor patch: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
• CISA directive deadline: 2026-04-08 — this is the mandatory deadline for US federal civilian agencies under BOD 22-01. All organizations should treat this date as a strong target regardless of federal mandate.
• Verify remediation: After patching, confirm the correct version is installed on all affected hosts. Run a vulnerability scan or use your asset management tooling to verify — do not rely solely on change tickets.

Detection Coverage

• Unauthenticated exploitation monitoring: Because this vulnerability requires no authentication, internet-facing scanning and exploitation attempts may begin within hours of public disclosure. Ensure alerting is in place before the end of the day.
• Threat intelligence feeds: Monitor your TI feeds and vendor advisory channels for published indicators of compromise (IOCs), proof-of-concept exploit releases, or active campaign reporting associated with this CVE — these should trigger an immediate hunt even if no internal alerts have fired.

Vulnerability Details

Additional Notes

https://github.com/langflow-ai/langflow/security/advisories/GHSA-vwmf-pq79-vjvx ; https://nvd.nist.gov/vuln/detail/CVE-2026-33017