CVE-2026-30821

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.

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.

Vulnerability Description

Vulnerability Overview

• 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).

Vulnerable Code

• Upload Route Definition

  https://github.com/FlowiseAI/Flowise/blob/d17c4394a238b49327b493c89feee45f3a20bb91/packages/server/src/routes/attachments/index.ts#L7-L10

  // CREATE
  router.post('/:chatflowId/:chatId', getMulterStorage().array('files'), attachmentsController.createAttachment)
  export default router
  

• Mount /api/v1/attachments to the global router

  https://github.com/FlowiseAI/Flowise/blob/d17c4394a238b49327b493c89feee45f3a20bb91/packages/server/src/routes/index.ts#L72-L77

  const router = express.Router()
  router.use('/ping', pingRouter)
  router.use('/apikey', apikeyRouter)
  router.use('/assistants', assistantsRouter)
  router.use('/attachments', attachmentsRouter)
  

• Include /api/v1/attachments in the WHITELIST_URLS list

  https://github.com/FlowiseAI/Flowise/blob/d17c4394a238b49327b493c89feee45f3a20bb91/packages/server/src/utils/constants.ts#L6-L26

  export const WHITELIST_URLS = [
      '/api/v1/verify/apikey/',
      '/api/v1/chatflows/apikey/',
      '/api/v1/public-chatflows',
      '/api/v1/public-chatbotConfig',
      '/api/v1/public-executions',
      '/api/v1/prediction/',
      '/api/v1/vector/upsert/',
      '/api/v1/node-icon/',
      '/api/v1/components-credentials-icon/',
      '/api/v1/chatflows-streaming',
      '/api/v1/chatflows-uploads',
      '/api/v1/openai-assistants-file/download',
      '/api/v1/feedback',
      '/api/v1/leads',
      '/api/v1/get-upload-file',
      '/api/v1/ip',
      '/api/v1/ping',
      '/api/v1/version',
      '/api/v1/attachments',
      '/api/v1/metrics',
  

• Bypass JWT validation if the URL is whitelisted

  https://github.com/FlowiseAI/Flowise/blob/d17c4394a238b49327b493c89feee45f3a20bb91/packages/server/src/index.ts#L213-L228

          const denylistURLs = process.env.DENYLIST_URLS ? process.env.DENYLIST_URLS.split(',') : []
          const whitelistURLs = WHITELIST_URLS.filter((url) => !denylistURLs.includes(url))
          const URL_CASE_INSENSITIVE_REGEX: RegExp = /\/api\/v1\//i
          const URL_CASE_SENSITIVE_REGEX: RegExp = /\/api\/v1\//
  
          await initializeJwtCookieMiddleware(this.app, this.identityManager)
  
          this.app.use(async (req, res, next) => {
              // Step 1: Check if the req path contains /api/v1 regardless of case
              if (URL_CASE_INSENSITIVE_REGEX.test(req.path)) {
                  // Step 2: Check if the req path is casesensitive
                  if (URL_CASE_SENSITIVE_REGEX.test(req.path)) {
                      // Step 3: Check if the req path is in the whitelist
                      const isWhitelisted = whitelistURLs.some((url) => req.path.startsWith(url))
                      if (isWhitelisted) {
                          next()
  

• Multer…

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.

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.

Vulnerability Description

Vulnerability Overview

• 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).

Vulnerable Code

• Upload Route Definition

  https://github.com/FlowiseAI/Flowise/blob/d17c4394a238b49327b493c89feee45f3a20bb91/packages/server/src/routes/attachments/index.ts#L7-L10

  // CREATE
  router.post('/:chatflowId/:chatId', getMulterStorage().array('files'), attachmentsController.createAttachment)
  export default router
  

• Mount /api/v1/attachments to the global router

  https://github.com/FlowiseAI/Flowise/blob/d17c4394a238b49327b493c89feee45f3a20bb91/packages/server/src/routes/index.ts#L72-L77

  const router = express.Router()
  router.use('/ping', pingRouter)
  router.use('/apikey', apikeyRouter)
  router.use('/assistants', assistantsRouter)
  router.use('/attachments', attachmentsRouter)
  

• Include /api/v1/attachments in the WHITELIST_URLS list

  https://github.com/FlowiseAI/Flowise/blob/d17c4394a238b49327b493c89feee45f3a20bb91/packages/server/src/utils/constants.ts#L6-L26

  export const WHITELIST_URLS = [
      '/api/v1/verify/apikey/',
      '/api/v1/chatflows/apikey/',
      '/api/v1/public-chatflows',
      '/api/v1/public-chatbotConfig',
      '/api/v1/public-executions',
      '/api/v1/prediction/',
      '/api/v1/vector/upsert/',
      '/api/v1/node-icon/',
      '/api/v1/components-credentials-icon/',
      '/api/v1/chatflows-streaming',
      '/api/v1/chatflows-uploads',
      '/api/v1/openai-assistants-file/download',
      '/api/v1/feedback',
      '/api/v1/leads',
      '/api/v1/get-upload-file',
      '/api/v1/ip',
      '/api/v1/ping',
      '/api/v1/version',
      '/api/v1/attachments',
      '/api/v1/metrics',
  

• Bypass JWT validation if the URL is whitelisted

  https://github.com/FlowiseAI/Flowise/blob/d17c4394a238b49327b493c89feee45f3a20bb91/packages/server/src/index.ts#L213-L228

          const denylistURLs = process.env.DENYLIST_URLS ? process.env.DENYLIST_URLS.split(',') : []
          const whitelistURLs = WHITELIST_URLS.filter((url) => !denylistURLs.includes(url))
          const URL_CASE_INSENSITIVE_REGEX: RegExp = /\/api\/v1\//i
          const URL_CASE_SENSITIVE_REGEX: RegExp = /\/api\/v1\//
  
          await initializeJwtCookieMiddleware(this.app, this.identityManager)
  
          this.app.use(async (req, res, next) => {
              // Step 1: Check if the req path contains /api/v1 regardless of case
              if (URL_CASE_INSENSITIVE_REGEX.test(req.path)) {
                  // Step 2: Check if the req path is casesensitive
                  if (URL_CASE_SENSITIVE_REGEX.test(req.path)) {
                      // Step 3: Check if the req path is in the whitelist
                      const isWhitelisted = whitelistURLs.some((url) => req.path.startsWith(url))
                      if (isWhitelisted) {
                          next()
  

• Multer…