CVE-2026-30821

What it is

Flowise is a drag & drop user interface to build a customized large language model flow. Prior to version 3.0.13, the /api/v1/attachments/:chatflowId/:chatId endpoint is listed in WHITELIST_URLS, allowing unauthenticated access to the file upload API. While the server validates uploads based on the MIME types defined in chatbotConfig.fullFileUpload.allowedUploadFileTypes, it implicitly trusts the client-provided Content-Type header (file.mimetype) without verifying the file's actual content (magic bytes) or extension (file.originalname). Consequently, an attacker can bypass this restriction by spoofing the Content-Type as a permitted type (e.g., application/pdf) while uploading malicious scripts or arbitrary files. Once uploaded via addArrayFilesToStorage, these files persist in backend storage (S3, GCS, or local disk). This vulnerability serves as a critical entry point that, when chained with other features like static hosting or file retrieval, can lead to Stored XSS, malicious file hosting, or Remote Code Execution (RCE). This issue has been patched in version 3.0.13.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data tampering.

Exploit odds

16.7% chance of exploitation in the next 30 days (EPSS). Higher than most.

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-03-07 05:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 10:32 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 16.7% in the next 30 days (EPSS).
• Severity: 8.2 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-03-07 05:16 UTC

Last modified

2026-06-17 10:32 UTC

Exploit probability

16.7% · EPSS, next 30 days

Weakness

CWE-434 · Unrestricted file upload

Record status

Analyzed

Affected

• Flowiseai Flowise < 3.0.13

Attack profile CVSS 4.0 · 8.2

Attack vector

Network

Complexity

High

Attack requirements

Present

Privileges needed

None

User interaction

None

Confidentiality

None

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-30821.md and follow it. Check whether this project is affected by CVE-2026-30821. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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