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CVE-2026-30821— Flowise: Arbitrary File Upload via MIME Spoofing

Quick assessment

Affected
FlowiseAI Flowise
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Flowise是FlowiseAI开源的一个用于轻松构建 LLM 应用程序的工具。 Flowise 3.0.13之前版本存在代码问题漏洞，该漏洞源于/api/v1/attachments/:chatflowId/:chatId端点未经验证即可访问，且未验证文件实际内容，可能导致存储型跨站脚本、恶意文件托管或远程代码执行。

AI Predicted 8.8 Difficulty: Easy EPSS 0.93% · P59

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application
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I. Basic Information for CVE-2026-30821

Vulnerability Information
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Vulnerability Title
Flowise: Arbitrary File Upload via MIME Spoofing
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
危险类型文件的不加限制上传
Source: CVE Program / CVE List V5
Vulnerability Title
Flowise 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Flowise是FlowiseAI开源的一个用于轻松构建 LLM 应用程序的工具。 Flowise 3.0.13之前版本存在代码问题漏洞，该漏洞源于/api/v1/attachments/:chatflowId/:chatId端点未经验证即可访问，且未验证文件实际内容，可能导致存储型跨站脚本、恶意文件托管或远程代码执行。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
FlowiseAI Flowise < 3.0.13 -

II. Public POCs for CVE-2026-30821

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III. Intelligence Information for CVE-2026-30821

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Patches & Fixes for CVE-2026-30821 (1)

Vendor Advisories for CVE-2026-30821 (1)

Same Patch Batch · FlowiseAI · 2026-03-07 · 5 CVEs total

CVE-2026-30820 Flowise Authorization Bypass via Spoofed x-request-from Header
CVE-2026-30824 Flowise: Missing Authentication on NVIDIA NIM Endpoints
CVE-2026-30823 Flowise: IDOR leading to Account Takeover and Enterprise Feature Bypass via SSO Configurat
CVE-2026-30822 Flowise: Mass Assignment in `/api/v1/leads` Endpoint

IV. Related Vulnerabilities

Same product: Flowise
Same vendor: FlowiseAI
Same weakness: CWE-434

V. Comments for CVE-2026-30821

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