FlowiseAI Flowise up to 3.0.12 /api/v1/attachments/ unrestricted upload

Summaryinfo

A vulnerability classified as critical was found in FlowiseAI Flowise up to 3.0.12. The affected element is an unknown function of the file /api/v1/attachments/. The manipulation results in unrestricted upload. This vulnerability was named CVE-2026-30821. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability, which was classified as critical, was found in FlowiseAI Flowise up to 3.0.12. Affected is an unknown function of the file /api/v1/attachments/. The manipulation with an unknown input leads to a unrestricted upload vulnerability. CWE is classifying the issue as CWE-434. The product allows the attacker to upload or transfer files of dangerous types that can be automatically processed within the product's environment. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-30821 since 03/05/2026. The exploitability is told to be difficult. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1608.002.

Upgrading to version 3.0.13 eliminates this vulnerability. The upgrade is hosted for download at github.com.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-0626). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

• Open Source Flowise

Productinfo

Vendor

• FlowiseAI

Name

• Flowise

Version

• 3.0.0
• 3.0.1
• 3.0.2
• 3.0.3
• 3.0.4
• 3.0.5
• 3.0.6
• 3.0.7
• 3.0.8
• 3.0.9
• 3.0.10
• 3.0.11
• 3.0.12

Website

• Product: https://github.com/FlowiseAI/Flowise/

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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