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CVE-2025-34291: Langflow Origin Validation Error Vulnerability

CVE-2025-34291 is rated critical with a CVSS v4.0 base score of 9.4 and affects Langflow Langflow. Per its scoring, it can be exploited over the network, without authentication. The scored impact on confidentiality, integrity and availability is the highest available. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-05-21, which means exploitation in the wild has been observed.

Vulnerability description

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.

Severity breakdown

CVSS v4.0 9.4: 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

  • Attack vector: Network. Exploitable remotely over the network.
  • Attack complexity: Low. No special conditions; the attack can be repeated reliably.
  • Attack requirements: None. No deployment or execution conditions are needed.
  • Privileges required: None. No account or prior access is needed.
  • User interaction: Passive. A user takes limited, routine action.
  • Confidentiality impact (vulnerable system): High. Total loss of confidentiality.
  • Integrity impact (vulnerable system): High. Total loss of integrity.
  • Availability impact (vulnerable system): High. Total loss of availability.
  • Confidentiality impact (subsequent systems): High. Total loss of confidentiality on other systems.
  • Integrity impact (subsequent systems): High. Total loss of integrity on other systems.
  • Availability impact (subsequent systems): High. Total loss of availability of other systems.

Underlying weakness

CWE-346: Origin Validation Error

The product does not properly verify that the source of data or communication is valid.

Affected products

  • Langflow: up to and including 1.6.9

References