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Unauthenticated Unrestricted File Upload in Langflow
CVE-2026-55450 is a critical missing-authentication vulnerability in Langflow versions earlier than 1.9.1. A deprecated upload API function accepted uploads without verifying requester credentials or validating the referenced flow identifier. It also lacked effective upload-size controls, allowing unauthenticated remote users to submit arbitrary volumes of data. Responses disclose the absolute filesystem location assigned to an uploaded file, exposing server directory-layout information.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
An unauthenticated attacker can exhaust host storage by repeatedly uploading data, causing denial of service for Langflow and potentially other processes sharing the filesystem. The absolute-path disclosure provides environmental information that may assist chaining with other vulnerabilities or attack primitives.
If you can’t patch tonight, do this now.
Until upgrading, restrict network access to Langflow to trusted users and networks; disable or block the deprecated upload API where operationally feasible; enforce request-body and upload-size limits at a reverse proxy or WAF; and monitor storage consumption and anomalous upload activity for attempted exhaustion.
Patch, then assume compromise.
Upgrade Langflow to version 1.9.1 or later. The fixed release requires authenticated ownership access for uploads and enforces a maximum file-upload size.
1 exploit validated by Mallory's analysis.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
9 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.