Langflow Security Vulnerability Still Actively Exploited: Here's What You Need to Do
If your business uses Langflow for AI application development, you need to address CVE-2025-34291 immediately. This vulnerability was added to the CISA Known Exploited Vulnerabilities catalog on May 21, 2026, and remains under active attack. The deadline for remediation has passed, which means if you haven't patched yet, your systems are sitting in the window where attackers are actively trying to break in. This isn't a future problem—it's a today problem.
What the Vulnerability Actually Does
Langflow has a CORS (Cross-Origin Resource Sharing) configuration that's too permissive, paired with a refresh token cookie set to SameSite=None. Individually, these are configuration choices. Together, they create a hole. An attacker can host a malicious webpage that tricks your users into visiting it. Once there, the attacker's page makes requests back to your Langflow instance on behalf of your logged-in users—and the browser allows it because of how the CORS and cookie settings are configured. The attacker then grabs the refresh tokens and uses them to access your authenticated endpoints.
This means full system compromise. We're not talking about reading a file or viewing some data. An attacker with these tokens can execute arbitrary code on your Langflow installation and potentially move laterally into your broader infrastructure. The path from token theft to complete takeover is short and well-understood by attackers.
Why Detection Is Harder Than You Think
The real problem here isn't technical complexity—it's the gap between knowing about a vulnerability and actually owning the remediation. Many small business owners assume their IT person or cloud provider has handled this. Your cloud provider probably hasn't, because it's your responsibility to patch the Langflow application you deployed. Your IT person might not know you're running Langflow at all. That gap is where breaches live.
Three Actions to Take Right Now
Step 1: Verify You're Running Langflow
Audit your infrastructure to confirm whether Langflow is actually deployed in your environment. Check your cloud consoles, your development servers, and ask your technical team directly. Document where every instance is running. Many organizations have applications deployed by developers that don't appear on official asset lists—this is a good time to close that gap.
Step 2: Apply Vendor Mitigations or Upgrade
Visit the official Langflow security advisories and follow the vendor's published guidance. This typically means either updating to a patched version or implementing the recommended configuration changes to your CORS settings and cookie behavior. If your version is no longer supported by the vendor, you need to make an upgrade decision immediately. The deadline for this remediation has passed, so any delay is adding risk.
Step 3: Check for Unauthorized Access
Review your Langflow logs for refresh token usage spikes or authentication activity from unfamiliar IP addresses. Look for any API calls to authenticated endpoints that shouldn't have been made. If you find suspicious activity, assume compromise and treat it as a full incident. This means rotating credentials, reviewing what data an attacker might have accessed, and notifying relevant parties.