CISA Adds Langflow Origin Validation Flaw to Known Exploited Vulnerabilities Catalog

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added a critical Langflow vulnerability, tracked as CVE-2025-34291, to its Known Exploited Vulnerabilities (KEV) Catalog, highlighting active exploitation risks and urging immediate remediation.

The vulnerability stems from an origin validation flaw in Langflow, a popular tool used for building and orchestrating AI-driven workflows.

According to CISA, the issue arises due to an overly permissive Cross-Origin Resource Sharing (CORS) configuration combined with insecure cookie settings. Specifically, the application uses refresh token cookies configured with SameSite=None, allowing them to be sent in cross-origin requests.

Langflow Origin Validation Flaw

The flaw is classified under CWE-346 (Origin Validation Error) and enables attackers to exploit trust boundaries between domains. By leveraging this misconfiguration, a malicious webpage can issue cross-origin requests that include user credentials.

Key technical aspects include:

• Improper origin validation allows unauthorized domains to interact with backend services.
• CORS policy is overly permissive, failing to restrict trusted origins.
• Refresh tokens are stored in cookies with SameSite=None, making them accessible in cross-site requests.
• Attackers can invoke the refresh endpoint and obtain valid authentication tokens.

Once a threat actor obtains these tokens, they can access authenticated endpoints and potentially execute arbitrary code within the system. This could lead to full system compromise depending on the privileges associated with the compromised account.

Although CISA has not confirmed whether CVE-2025-34291 is currently used in ransomware campaigns, its inclusion in the KEV catalog indicates active exploitation in the wild. Vulnerabilities involving authentication bypass and token theft are often leveraged in post-exploitation stages, including lateral movement and persistence.

Successful exploitation could allow attackers to:

• Hijack user sessions.
• Access sensitive workflows and data.
• Execute unauthorized actions within Langflow environments.
• Escalate privileges and compromise the underlying infrastructure.

CISA has mandated federal agencies to remediate this vulnerability by June 4, 2026, under Binding Operational Directive (BOD) 22-01. Organizations using Langflow are strongly advised to take immediate action.

Recommended mitigation steps include:

• Apply security patches or updates provided by the vendor.
• Restrict CORS policies to trusted origins only.
• Configure cookies with secure attributes such as SameSite=Strict or Lax.
• Review authentication mechanisms and token handling practices.
• Monitor logs for suspicious cross-origin requests and token misuse.

If no patches or mitigations are available, CISA advises discontinuing the use of affected systems until the issue is resolved.

This vulnerability highlights the growing risk posed by misconfigured CORS policies in modern web applications, particularly those that handle authentication tokens. As attackers continue to target weak trust boundaries, organizations must ensure strict validation of origins and secure session management practices.

The addition of CVE-2025-34291 to the KEV catalog underscores the urgency for organizations to audit their web security configurations and prioritize remediation to prevent potential exploitation.

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