Flowise Evaluation Mass Assignment Vulnerability

Executive Summary

CVE-2026-46479 is a high-severity vulnerability in Flowise versions up to 3.1.1 that involves mass-assignment through Object.assign() in the Evaluation controller/service.

This vulnerability allows authenticated users with low privileges (edit permissions) to overwrite critical fields such as workspaceId and id during create or update operations.

By manipulating these fields, an attacker can perform a cross-workspace evaluation takeover, effectively moving an evaluation from one workspace to another without authorization.

The root cause is that the server does not properly validate or restrict client-controlled fields, and workspace UUIDs are exposed in API responses, making it easy for attackers to enumerate target workspaces.

This issue has been patched in version 3.1.2 by replacing the unsafe Object.assign() with an explicit allowlist pattern to prevent unauthorized persistence of client-controlled fields.

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Impact Analysis

This vulnerability can have significant impacts on confidentiality, integrity, and availability of data within Flowise.

An attacker with low privileges can take over evaluations across different workspaces, potentially accessing or modifying data they should not have access to.

Such unauthorized cross-workspace data takeover can lead to data breaches, unauthorized data manipulation, and disruption of normal operations.

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Detection Guidance

This vulnerability can be detected by monitoring API requests to the Flowise Evaluation controller/service for suspicious mass-assignment attempts where fields like workspaceId and id are being overwritten during create or update operations.

Since workspace UUIDs are exposed in API responses, an attacker might enumerate workspaces by analyzing API traffic.

To detect exploitation attempts, you can log and inspect HTTP requests that include changes to workspaceId or id fields in evaluation create or update endpoints.

Example commands to monitor such activity might include using tools like curl or tcpdump to capture traffic, or grep to search logs for suspicious parameter changes.

• Use grep to find requests modifying workspaceId or id in server logs: grep -iE 'workspaceId|id' /path/to/flowise/logs/access.log
• Use tcpdump to capture HTTP traffic on the server port (e.g., 80 or 443): tcpdump -A -s 0 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'
• Use curl to manually test if workspaceId or id can be overwritten by sending crafted POST or PUT requests to evaluation endpoints.

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Mitigation Strategies

The immediate step to mitigate this vulnerability is to upgrade Flowise to version 3.1.2 or later, where the issue has been patched.

The patch replaces unsafe mass-assignment via Object.assign() with an explicit allowlist pattern that prevents client-controlled fields like workspaceId and id from being overwritten.

Until the upgrade can be applied, restrict access to the Evaluation create and update APIs to trusted users only, and monitor for suspicious activity involving workspaceId or id modifications.

Additionally, review and tighten permissions to ensure only users with appropriate privileges can perform evaluation edits.

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Compliance Impact

The vulnerability allows authenticated users with low privileges to perform cross-workspace evaluation takeover by manipulating critical fields such as workspaceId. This leads to unauthorized access and modification of data across different workspaces, constituting an Insecure Direct Object Reference (IDOR) vulnerability.

Such unauthorized access and data manipulation can compromise the confidentiality and integrity of sensitive information, which are key requirements under common standards and regulations like GDPR and HIPAA.

Therefore, if exploited, this vulnerability could lead to non-compliance with these regulations due to potential unauthorized data exposure and modification.

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