Langflow Langflow
CVE-2025-34291
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.
What this means for your business
- It affects Langflow. It matters if your company, or a supplier that handles your data, runs it.
- Attackers are already using it. CISA added it to its list of flaws used in real attacks on 21 May 2026.
- An attacker can use it remotely, over a network, with an ordinary user login, and without anyone at your company clicking anything.
- FIRST's prediction model gives it a 93% chance of attack attempts being seen in the next 30 days, ranking above 99% of all known flaws.
What to do
- 1Check whether your company or your suppliers run Langflow, and which version. The affected versions are listed further down this page.
- 2If you do, follow CISA's required action below. No patch reference has been published yet.
- 3Treat it as urgent. US federal agencies must fix it by 4 June 2026. That deadline does not apply to private companies, but it shows how seriously CISA takes it.
- 4Because attackers have used it, check the affected systems for signs of a break-in, not only for the update.
Fastnexa security experts
Attackers are already using this flaw. Is your Langflow Langflow exposed?
Tell us where you run Langflow Langflow and a Fastnexa penetration tester will check whether this flaw, or others like it, can be used against your websites, apps and network.
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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’s wording, unedited.
Scoring
- CVSS
- 8.8 (v3.1)
- Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H- CVSS v4
- 9.4
- Weakness
- CWE-346
- Assigned by
- disclosure@vulncheck.com
Dates
- Published
- 2026-05-21
- Last modified
- 2026-10-15
- Added to KEV
- 2026-05-21
- Remediation due
- 2026-06-04
- Sources
- CISA KEV, NVD
Affected products
- Langflow Langflow- 1.6.9
As listed in the NVD configuration data. Not a statement about your estate.
References
- https://github.com/langflow-ai/langflow
- https://www.obsidiansecurity.com/blog/cve-2025-34291-critical-account-takeover-and-rce-vulnerability-in-the-langflow-ai-agent-workflow-platform
- https://www.vulncheck.com/advisories/langflow-cors-misconfiguration-to-token-hijack-and-rce
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-34291
- https://www.crowdsec.net/vulntracking-report/cve-2025-34291