CVE intelligence and bounded remediation

CVE-2026-30821 — Flowise is a drag & drop user interface to build a customized large language model flow

Critical CVSS 9.8

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.

Severity
Critical
CVSS
9.8 (3.1)
Published
2026-03-07
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-434

Affected products

  • flowiseai / flowise

Matched remediation archetype

Path traversal, unsafe upload, and file handling

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Check exposure

  • Trace untrusted filenames, archive entries, URLs, and path segments into read, write, include, extraction, and upload operations.
  • Identify filesystem roots, mount permissions, symbolic-link behavior, archive handling, and whether uploaded content is web-accessible or executable.
  • Review canonicalization and containment checks across supported operating systems and storage backends.

Remediate safely

  • Generate server-side storage identifiers and resolve paths beneath a fixed root using filesystem-aware containment checks.
  • Reject absolute, parent-relative, alternate-separator, device, link, and archive entries that escape the intended root.
  • Store uploads outside executable or served paths, validate type and size, and use private atomic temporary files.

Authoritative sources

Complete CVE record and remediation plan

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