Security Digest · Vulnerability record
CVE-2026-33309: Langflow has an Arbitrary File Write (RCE) via v2 API
Langflow is a tool for building and deploying AI-powered agents and workflows.
CVSS 10.0 Critical EPSS 1.1% · p65
Should you act?
Critical, preconditions apply
Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 1.1%, percentile 65: FIRST’s model estimates a 1.1% chance of exploitation activity in the next 30 days, higher than 65% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes
langflow(PyPI) >= 1.2.0, < 1.9.0, fixed in 1.9.0. Check your lockfile, including transitive dependencies.
What it is
Langflow is a tool for building and deploying AI-powered agents and workflows. Versions 1.2.0 through 1.8.1 have a bypass of the patch for CVE-2025-68478 (External Control of File Name), leading to the root architectural issue within LocalStorageService remaining 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). Version 1.9.0 contains an updated fix.
From the GitHub advisory
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:
1. 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. 2. 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.
Weakness type: CWE-22, CWE-73, CWE-94, CWE-284.
Product: langflow (PyPI) · Assigned by: GitHub_M · Published: 2026-03-24
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| PyPI | langflow | >= 1.2.0, < 1.9.0 | 1.9.0 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| langflow-ai | langflow | >= 1.2.0, < 1.9.0 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 10 Critical | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
| GitHub | 3.1 | 9.9 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: low (any account)
- User interaction: none
- Scope: changed (can affect other components)
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable no, technical impact total.
- FIRST EPSS (model of 2026-10-21): 1.09% probability of exploitation activity in the next 30 days; percentile 65.
Timeline
- — GitHub-reviewed advisory GHSA-g2j9-7rj2-gm6c published (critical)
- — CVE record published by GitHub_M
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-g2j9-7rj2-gm6c github.com
- CVE.org record CVE-2026-33309 cve.org
- NVD entry CVE-2026-33309 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com