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Actively exploited

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.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 21 May 2026.
  • Rated Critical severity (CVSS 9.4, scored by Vendor).
  • It has been in the catalogue for 169 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

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.

Affected Versions

ProductVersions
Langflow Langflow1.6.9 and earlier

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for Langflow. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

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

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated critical, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 4 Jun 2026 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited Langflow Flaws

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CVE-2026-0770Langflow Inclusion of Functionality from Untrusted Control Sphere VulnerabilityAdded 21 Jul 2026CVE-2026-55255Langflow Authorization Bypass Through User-Controlled Key VulnerabilityAdded 7 Jul 2026CVE-2026-33017Langflow Code Injection VulnerabilityAdded 25 Mar 2026CVE-2025-3248 · RansomwareLangflow Missing Authentication VulnerabilityAdded 5 May 2025

All 5 exploited Langflow vulnerabilities

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2025-34291
  3. CVE record: CVE-2025-34291
  4. FIRST EPSS
  5. github.com/langflow-ai/langflow/releases/tag/v1.9.3
  6. github.com/langflow-ai/langflow/issues/11465#event-25774545848
  7. obsidiansecurity.com/blog/cve-2025-34291-critical-account-takeover-and-rce-vulnerability-in-the-lang
  8. github.com/langflow-ai/langflow
  9. vulncheck.com/advisories/langflow-cors-misconfiguration-to-token-hijack-and-rce