Authenticated Path Traversal Arbitrary File Write in Langflow Files API
CVSS 3.1
8.8high
EPSS
36%p98
Published
()
Modified
AI analysis
CVE-2026-5027 is a path traversal flaw (CWE-22) in the 'POST /api/v2/files' endpoint of Langflow, the open-source platform for building AI/LLM agent workflows. The endpoint fails to sanitize the 'filename' field supplied in multipart form data, so an attacker who submits a name containing '../' sequences can direct the resulting file write to arbitrary locations on the server's filesystem. The CVSS vector (network-accessible, low complexity, low-privilege account required, no user interaction) indicates an authenticated user can abuse this to overwrite or create files at attacker-chosen paths, which can compromise confidentiality, integrity, and availability — for example by overwriting configuration, credentials, or executable content that leads to code execution depending on deployment. Any organization running a self-hosted Langflow instance that exposes the files API, even to low-privileged accounts, is affected. No public proof-of-concept or confirmed in-the-wild exploitation is known for this specific CVE, and it is not yet on CISA's KEV list, but its elevated EPSS (36.1%, 98th percentile) and active exploitation of other Langflow vulnerabilities (e.g., CVE-2026-0768) suggest near-term exploitation risk.
What to do: Upgrade Langflow to the latest patched release per the vendor advisory (specific fixed version is not stated in the available data). Until patched, restrict access to /api/v2/files to trusted, authenticated users, place Langflow behind authentication/reverse-proxy filtering that strips or validates '..' sequences in multipart filenames, and avoid exposing the instance directly to the internet. Review access logs for multipart POST requests to /api/v2/files with filenames containing '../' that could indicate attempted traversal writes.
Affected
langflow
—
Estimated exposure
moderatelikely tens of thousands of self-hosted deployments, with thousands of internet-exposed instances — Langflow is a widely adopted open-source AI workflow builder, and public internet scans during earlier Langflow vulnerability waves showed thousands of exposed instances, implying a moderate (roughly 10k–100k) installed base rather than a…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
The 'POST /api/v2/files' endpoint does not sanitize the 'filename' parameter from the multipart form data, allowing an attacker to write files to arbitrary locations on the filesystem using path traversal sequences ('../').
VulnCheck reports active exploitation of critical Langflow CVE-2026-0768 and Rails CVE-2026-66066 for credential harvesting, with detections rising to 360.
VulnCheck observed active exploitation of CVE-2026-0768 (CVSS 9.8) in Langflow and CVE-2026-66066 'KindaRails2Shell' (CVSS 9.5) in Ruby on Rails, with detections rising from 50 on August 30, 2026 to 360 by September 1. The Rails flaw allows unauthenticated arbitrary file reads, leaking secret_key_base, Rails master key, database passwords, cloud credentials and API tokens, ultimately enabling RCE; the patch still leaves the variation-key Marshal deserialization RCE gadget functional. Observed chains include a Python credential harvester with SimpleHelp remote access via CVE-2026-5027, and weaponization of CVE-2025-3248 to enlist hosts into an XMR mining botnet after disabling auditd. More than 7,100 exposed vulnerable Ruby on Rails instances and over 15,000 successful exploitation attempts across three Langflow flaws were recorded.
Critical CVSS 9.8 RCE CVE-2026-0768 in Langflow is under active exploitation, with attackers probing for credentials and secrets.
CVE-2026-0768, a critical (CVSS 9.8) remote code execution flaw in Langflow's code validator, lets attackers execute Python code with root privileges via the validate endpoint's code parameter. VulnCheck honeypots in the UK detected Russian-origin exploitation performing reconnaissance and credential harvesting, querying environment variables like LANGFLOW_SUPERUSER and AWS keys and reading Langflow's secret key. Versions before 1.4.2 are affected; no vendor advisory or public PoC was available at reporting time.