Authorization bypass through user-controlled key in Langflow - CVE-2026-55255
Published: June 19, 2026
Vulnerability identifier: #VU134972
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-55255
CWE-ID: CWE-639
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Langflow
Affected software:
Langflow
Langflow
Detailed vulnerability description
The vulnerability allows a remote user to execute another user's flow and disclose sensitive information.
The vulnerability exists due to improper access control in the /api/v1/responses endpoint and get_flow_by_id_or_endpoint_name helper function when handling requests that reference a flow by UUID. A remote user can send a specially crafted request with a victim's flow ID to execute another user's flow and disclose sensitive information.
The issue occurs only for UUID-based flow lookups; endpoint_name-based lookups apply a user ownership check.
How to mitigate CVE-2026-55255
Install security update from vendor's website.