CVE-2026-33309 is a critical-severity path traversal vulnerability in langflow (pip), affecting versions >= 1.2.0, < 1.9.0. It is fixed in 1.9.0.
Summary While reviewing the recent patch for CVE-2025-68478 (External Control of File Name in v1.7.1), I discovered that the root architectural issue within LocalStorageService remains unresolved. Because the underlying storage layer lacks boundary containment checks, the system relies entirely on the HTTP-layer ValidatedFileName dependency. This defense-in-depth failure leaves the POST /api/v2/files/ endpoint vulnerable to Arbitrary File Write. The multipart upload filename bypasses the path-parameter guard, allowing authenticated attackers to write files anywhere on the host system, leading to Remote Code Execution (RCE). Details The vulnerability exists in two layers: API Layer (src/backend/base/langflow/api/v2/files.py:162): Inside the uploaduserfile route, the filename is extracted directly from the multipart Content-Disposition header (newfilename = file.filename). It is passed verbatim to the storage service. ValidatedFileName provides zero protection here as it only guards URL path parameters. Storage Layer (src/backend/base/langflow/services/storage/local.py:114-116): The LocalStorageService uses naive path concatenation (filepath = folderpath / filename). It lacks a resolve().isrelativeto(basedir) containment check. Recommended Fix: Sanitize the multipart filename before processing: Add a canonical path containment check inside LocalStorageService.savefile to permanently kill this vulnerability class. PoC This Python script verifies the vulnerability against langflowai/langflow:latest (v1.7.3) by writing a file outside the user's UUID storage directory. Server Logs: Docker cntainer file: Impact Authenticated Arbitrary File Write. An attacker can overwrite critical system files, inject malicious Python components, or overwrite .ssh/authorized_keys to achieve full Remote Code Execution on the host server.
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
CVE-2026-33309 has a CVSS score of 9.9 (Critical). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (1.9.0). Upgrading removes the vulnerable code path.
pip
langflow (>= 1.2.0, < 1.9.0)langflow → 1.9.0 (pip)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
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Upgrade langflow to 1.9.0 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-33309 is a critical-severity path traversal vulnerability in langflow (pip), affecting versions >= 1.2.0, < 1.9.0. It is fixed in 1.9.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
CVE-2026-33309 has a CVSS score of 9.9 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
langflow (pip) versions >= 1.2.0, < 1.9.0 is affected.
Yes. CVE-2026-33309 is fixed in 1.9.0. Upgrade to this version or later.
Whether CVE-2026-33309 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade langflow to 1.9.0 or later.