Langflow Origin Validation Error (CVE-2025-34291)

Historical catalog analysis: CISA added this entry on May 21, 2026. The entry reflects catalog information retrieved on August 31, 2026, not a snapshot archived on the inclusion date. Check current vendor guidance before acting.

What the vulnerability is

CVE-2025-34291 is an origin validation error within Langflow. The flaw stems from a combination of an overly permissive Cross-Origin Resource Sharing (CORS) configuration and a refresh token cookie set to SameSite=None. This configuration allows a malicious webpage to initiate cross-origin requests that include credentials to call the refresh endpoint. If successful, this could enable an attacker to obtain tokens for authenticated endpoints, potentially leading to arbitrary code execution and full system compromise.

Exposure and applicability

This vulnerability affects deployments of Langflow where the CORS and cookie configurations described are present. Because Langflow is an open-source component, this exposure may extend to various proprietary implementations or third-party products that integrate the software. Organizations utilizing Langflow for LLM orchestration should determine if their current version and configuration match the vulnerable state identified in CWE-346.

Remediation priorities

Based on our analysis, vulnerability management teams should prioritize the following actions:

1. Update Software: Prioritize upgrading to Langflow v1.9.3 or applying vendor-supplied mitigations to address the origin validation error.
2. Review CORS Policy: Audit current CORS settings to ensure they are not overly permissive and restrict requests to trusted origins only.
3. Audit Cookie Attributes: Verify that session and refresh tokens are not using SameSite=None unless strictly required and paired with other stringent security controls.

How to validate remediation

Verification must go beyond a simple version check, as configuration overrides may persist across updates. Defenders should verify the following:

• CORS Header Validation: Use authorized network inspection tools to confirm that the server no longer accepts cross-origin requests from untrusted domains.
• Cookie Attribute Inspection: Inspect the Set-Cookie headers for refresh tokens to ensure the SameSite attribute is set to a more restrictive value (e.g., Lax or Strict) rather than None.

Confirmation of these technical changes provides evidence that the specific exposure path has been reduced.

Limits and open questions

While updating to v1.9.3 addresses the reported flaw, residual risk remains if the environment relies on other permissive network configurations or if third-party integrations introduce similar origin validation gaps. It is currently unknown whether this vulnerability has been utilized in known ransomware campaigns. Furthermore, because Langflow can be embedded in various ways, the total footprint of affected assets may be difficult to identify without a comprehensive software bill of materials (SBOM).

Source and editorial note

CVE-2025-34291: Langflow Origin Validation Error Vulnerability · Source date: May 21, 2026 · Retrieved August 31, 2026.

Material facts are tied to the cited primary source. Recommendations are independent defensive analysis unless attributed to the source. Confirm consequential decisions against current authoritative guidance.

Archive date: May 24, 2026. The displayed post date is assigned three days after the source date to organize this retrospective archive; it does not mean this site published the analysis then. First published by this site: September 10, 2026 at 00:42 UTC.

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