Known exploited vulnerability · CISA KEV

CVE-2025-34291: Langflow Origin Validation Error Vulnerability

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.

CVE-2025-34291

Exploited in the wild. Fix this first.

CISA added it to the Known Exploited Vulnerabilities catalog on 2026-05-21: attackers are using it right now.

CISA KEV: Listed; Added 2026-05-21 · federal fix-by 2026-06-04
EPSS (30 days): 93%; Higher than 99.8% of CVEs · 2026-11-01
CVSS v4.0: 9.4 Critical; 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

What CISA says

Langflow Origin Validation Error Vulnerability

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

NVD description · published 2025-12-05

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.

Full record on NVD

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How to check if you are exposed to CVE-2025-34291

Find every Langflow system you or your clients run, including ones exposed to the internet. Those come first: CISA only lists flaws attackers are already using.
Compare each version with the fixed versions in the vendor advisory below. Where no fix exists yet, apply the vendor’s mitigation or take the system off the internet.
Run a credentialed vulnerability scan to catch the systems you missed, then check that the next scan no longer reports CVE-2025-34291.

US federal agencies had to fix this by 2026-06-04. Everyone else should treat that deadline as a guide: if it has passed, this is overdue.

Affected versions

Versions the National Vulnerability Database lists as vulnerable to CVE-2025-34291. Check the vendor advisory for the exact fixed builds before you sign anything off.

Product	Vulnerable versions
Langflow	up to and including 1.6.9

Timeline

2025-12-05 · Published in the National Vulnerability Database
2026-05-21 · Added to CISA's Known Exploited Vulnerabilities catalog, 167 days after it was published
2026-06-04 · Fix-by date for US federal agencies, passed 150 days ago

Vendor advisories and fixes

Weakness type

CWE-346

More exploited Langflow vulnerabilities

CISA lists 5 exploited Langflow vulnerabilities. The closest matches:

Keep going

Sources: CISA Known Exploited Vulnerabilities catalog (version 2026.10.30); EPSS data from FIRST.org; CVSS and descriptions from the NIST National Vulnerability Database. Checked 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.