Known exploited · Langflow
CVE-2025-34291: Langflow Origin Validation Error Vulnerability
What it is
Langflow contains an origin validation error vulnerability in which an overly permissive CORS configuration combined with a refresh token cookie configured as SameSite=None allows a malicious webpage to perform cross-origin requests that include credentials and successfully call the refresh endpoint. This could allow the attacker to execute arbitrary code and achieve full system compromise via obtained tokens that permit access to authenticated endpoints.
- Vendor
- Langflow
- Product
- Langflow
- Added to KEV
- May 21, 2026
- CISA due date
- June 4, 2026
- Ransomware use
- Unknown
- Weakness
- CWE-346: Origin Validation Error
What CISA requires
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Forensic triage
No
What to do now
- Find every instance of Langflow you run, including the forgotten ones, and check its version against the vendor advisory.
- Apply the vendor's fix or mitigation, before June 4, 2026 if you are bound by CISA's deadline, sooner if it faces the internet.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
References
H2 Security
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Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.