CVE-2025-34291: Langflow Origin Validation Error Vulnerability

In short

Langflow Langflow has a weakness classified as CWE-346. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-05-21. NVD lists CVSS 4.0 at 9.4 CRITICAL.

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.” — CISA KEV, retrieved 2026-11-01

“Langflow versions up to and including 1.6.9 contain a chained vulnerability that enables account takeover and remote code execution. An overly permissive CORS configuration (allow_origins='*' with allow_credentials=True) 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. An attacker-controlled origin can therefore obtain fresh access_token / refresh_token pairs for a victim session. Obtained tokens permit access to authenticated endpoints — including built-in code-execution functionality — allowing the attacker to execute arbitrary code and achieve full system compromise.” — NVD, retrieved 2026-11-01

Who is affected

Langflow Langflow. NVD lists the following versions as affected:

• Versions through 1.6.9

Exploitation status

CISA KEV added: 2026-05-21. Known ransomware campaign use: Not reported by CISA. Due date CISA set for US federal civilian agencies: 2026-06-04.

Scores

NVD CVSS 4.0: 9.4 CRITICAL; vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source [email protected].

EPSS by FIRST: 92.81%; percentile 99.83; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-346.

Timeline

CISA required action

“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 KEV

What to do

• Confirm whether you run Langflow Langflow and which version.
• Apply the vendor update or mitigation in the vendor advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Third Party Advisory: https://www.vulncheck.com/advisories/langflow-cors-misconfiguration-to-token-hijack-and-rce
• Third Party Advisory: https://www.crowdsec.net/vulntracking-report/cve-2025-34291
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.