Arbitrary file upload in Flowise - CVE-2026-30821
Published: April 9, 2026
Vulnerability identifier: #VU125532
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-30821
CWE-ID: CWE-434
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: FlowiseAI
Affected software:
Flowise
Flowise
Detailed vulnerability description
The vulnerability allows a remote attacker to upload arbitrary files.
The vulnerability exists due to unrestricted upload of file with dangerous type in the /api/v1/attachments/:chatflowId/:chatId endpoint when handling file upload requests that rely on the client-supplied Content-Type header. A remote attacker can send a specially crafted multipart/form-data request with a spoofed MIME type to upload arbitrary files.
The affected endpoint is whitelisted, allowing unauthenticated access, and uploaded files may persist in S3, GCS, or local storage.
How to mitigate CVE-2026-30821
Install security update from vendor's website.