CVE-2026-46476: Flowise: CustomTemplate create+update mass-assignment allows cross-workspace template takeover

Synopsis

A mass-assignment vulnerability in Flowise, the drag-and-drop LLM flow builder, allows an authenticated attacker to set arbitrary ownership fields when creating or updating a CustomTemplate, overwriting templates that belong to other workspaces. The vulnerability is reachable over the network and requires only a low-privilege account. Successful exploitation lets the attacker read, modify, or corrupt templates owned by other tenants, effectively taking over cross-workspace resources. HarborGuard tracks this advisory and will make a patched-image rebuild available the moment an upstream fix is published.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The vulnerable API endpoint is exposed over the network, so the attacker must be able to reach the Flowise service remotely.

• AuthenticationRequired

  Any low-privilege Flowise account is sufficient; no administrative or elevated credentials are needed.

• Victim interactionNot required

  The attacker can carry out the takeover entirely on their own without any action from another user.

• Attack complexityDetail

  The base exploit is condition-free and reliable, though the CVSS vector notes an attack requirement (AT:P), meaning specific deployment conditions such as multi-workspace configuration must be present for the cross-workspace takeover to be meaningful.

Blast Radius

• Reads the full content of CustomTemplates owned by other workspaces, exposing proprietary LLM flow definitions and any embedded credentials or prompts.
• Overwrites or corrupts CustomTemplates in other workspaces, breaking flows that other tenants depend on.
• Causes service disruption for affected workspaces if critical templates are deleted or replaced with malformed data.
• The confidentiality, integrity, and availability of tenant-scoped template data are all fully compromised on the vulnerable host.