CVE-2025-34291

CORS is a browser “rulebook” that tells websites which other sites they’re allowed to talk to. In Langflow versions up to 1.6.9, that rulebook is wrong, so an attacker can trick a user’s browser into handing over login access (token hijack), and then use that stolen access to run code on the server.

Think of it like leaving your office keycard reader set to accept keycards from the wrong door—then letting someone use that access to open the server room.

This matters if you run Langflow (self-hosted or otherwise exposed) and your Langflow version is 1.6.9 or older. The risk is tied to the vulnerable web behavior being reachable and usable over the network; findings indicate it is reachable in default configuration.

End-to-end risk is highest when the Langflow service is reachable from the internet or other untrusted networks without strong network access restrictions.

This is RED because it’s listed in CISA’s Known Exploited Vulnerabilities (KEV), meaning it’s known to be exploited in real environments. Attackers can hijack authentication tokens and then execute arbitrary code remotely, and this does not require a victim to take action.

Treat this as an immediate patch/mitigation task—upgrade to the fixed version without delay.

1. Confirm exposure

   • Determine how you access Langflow (direct internet URL, reverse proxy, internal-only, etc.).
   • Check the exact Langflow version running in production. This vulnerability applies to versions up to 1.6.9.
   • Confirm whether the service is reachable from untrusted networks (for example, the public internet) as the findings say it is reachable in default configuration.

2. Upgrade remediation (preferred)

   • Upgrade Langflow to 1.7.0 (the fixed version).
   • After upgrading, perform a quick functional check (UI loads, API endpoints respond, workflows still run).

3. Temporary mitigation if upgrade is delayed

   • Apply the vendor/workaround guidance available from the linked remediation reference provided in the findings.
   • In addition, restrict network access so the vulnerable web interface is not reachable from untrusted networks (for example, allow-list only your office/VPN IPs or internal networks through your reverse proxy/firewall).

4. Validate and monitor after the change

   • Review authentication/session logs for abnormal token usage patterns and unexpected login origins.
   • Look for signs of remote execution attempts around the time of any suspicious sessions (for example, unusual outbound connections or unexpected process activity tied to Langflow).

5. KEV timeline

   • CISA KEV listing: added 2026-05-21.
   • CISA remediation due date: 2026-06-04.

6. Keep an eye on follow-up advisories

   • Monitor for any additional guidance specific to your deployment method (reverse proxy, container setup, or authentication front-ends).

Severity is high (reported CVSS 8.8) and the attack is network-reachable with low attacker work: low privilege and no user interaction required. The underlying issue is a CORS misconfiguration (CWE-346) in Langflow versions up to 1.6.9, which can allow a malicious origin to abuse browser cross-origin behavior to steal authentication tokens (token hijack). Once an attacker has those tokens, they can perform actions as the victim and trigger remote code execution (arbitrary code execution) on the target server.

Exploitation status: This CVE is listed in CISA’s KEV (Known Exploited Vulnerabilities), indicating it has been observed/confirmed as exploited in the wild. A public exploit is also referenced in the findings, which increases practical attack likelihood.

Fix: The vendor-fixed version is Langflow 1.7.0.