Langflow: Unauthenticated file upload leads to DoS (space exhaustion) and information leak
Langflow
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- Severity
- Critical, CVSS 9.3
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:H
- Record
- CVE-2026-55450
- Affects
- Langflow
- Known exploited
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Published
- Record first published by the source
- June 23, 2026
- Source last modified
- October 25, 2026
Description
Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.1, unauthenticated users can upload any amount of data to the server without any limitations. No need for any prior knowledge, only network access to Langflow. This can lead to space exhaustion on the server. In addition, in the response, the absolute path of the uploaded file is reported to the attacker, which is an information leak that can assist in chaining other primitives. This vulnerability is fixed in 1.9.1.
Description quoted from the NVD record.
Who is affected
Your organization is affected if it runs Langflow, a tool for building and running apps and automated workflows that use AI language models. This flaw affects versions before 1.9.1. Anyone who can reach Langflow over a network can upload files to it without logging in and with no limit on how much data they send. An attacker could fill up the server's storage space, which can stop the server from working. After an upload, Langflow also tells the attacker exactly where the file was stored on the server, which could help them plan further attacks. This flaw is rated Critical.
What to do
- Find out who looks after Langflow for your organization: the person who installed or runs it, or the IT provider or vendor who manages it for you.
- If someone in your organization runs it, they should update Langflow to version
1.9.1or later, which fixes this flaw. - If an IT provider or vendor runs it for you, send them this advisory and ask when the update to version
1.9.1will be done. - After the update, ask whoever did it to check that Langflow now shows version
1.9.1or later.
Analysis written from the source record as of October 25, 2026 and reviewed before publishing.