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Luu, T.J.

GHSA-g2j9-7rj2-gm6c: Langflow has an Arbitrary File Write (RCE) via v2 API

criticalvulnerability

security

Source: GitHub Advisory DatabaseMarch 19, 2026CVE-2026-33309

Summary

Langflow's file upload endpoint (POST /api/v2/files/) is vulnerable to arbitrary file write (a type of attack that lets attackers save files anywhere on a server) because it doesn't properly validate filenames from multipart requests. Attackers who are logged in can use directory traversal characters (like "../") in filenames to write files outside the intended directory, potentially achieving RCE (remote code execution, where attackers can run commands on the server).

Solution / Mitigation

The source recommends two fixes: (1) Sanitize the multipart filename by extracting only the file name component and rejecting names containing "..": `new_filename = StdPath(file.filename or "").name` and add validation to reject invalid names. (2) Add a canonical path containment check inside `LocalStorageService.save_file` using `resolve().is_relative_to(base_dir)` to ensure files are always saved within the intended base directory.