CVE-2026-41277 Overview
CVE-2026-41277 is a Mass Assignment vulnerability affecting Flowise, a drag & drop user interface application used to build customized large language model (LLM) flows. Prior to version 3.1.0, the DocumentStore creation endpoint allows authenticated users to control the primary key (id) and internal state fields of DocumentStore entities through improper access control.
Because the service uses repository.save() with a client-supplied primary key, the POST create endpoint behaves as an implicit UPSERT operation, enabling overwriting of existing DocumentStore objects. In multi-workspace or multi-tenant deployments, this can lead to cross-workspace object takeover and broken object-level authorization (IDOR), allowing an attacker to reassign or modify DocumentStore objects belonging to other workspaces.
Critical Impact
Authenticated attackers can overwrite or hijack DocumentStore objects across workspaces in multi-tenant Flowise deployments, leading to data tampering and unauthorized access to LLM workflow configurations.
Affected Products
- Flowise versions prior to 3.1.0
- Multi-workspace Flowise deployments
- Multi-tenant Flowise installations
Discovery Timeline
- 2026-04-23 - CVE CVE-2026-41277 published to NVD
- 2026-04-23 - Last updated in NVD database
Technical Details for CVE-2026-41277
Vulnerability Analysis
This vulnerability stems from improper access control (CWE-284) in how Flowise handles DocumentStore entity creation. The core issue lies in the application's acceptance of client-supplied primary keys during object creation operations without proper validation or authorization checks.
When an authenticated user sends a POST request to the DocumentStore creation endpoint, they can specify the id field along with other internal state fields. The backend service directly passes this client-supplied data to repository.save(), which performs an UPSERT operation—creating a new record if the ID doesn't exist, or updating an existing record if it does.
This design flaw transforms a simple create operation into a potential weapon for cross-tenant attacks. An attacker who knows or can guess the ID of a DocumentStore object belonging to another workspace can effectively overwrite that object with their own data, breaking the intended access control boundaries.
Root Cause
The root cause is the lack of proper input validation and authorization controls in the DocumentStore creation endpoint. The application fails to:
- Prevent client-side specification of primary key (id) values during entity creation
- Validate that the requesting user has authorization to modify existing objects when an ID collision occurs
- Implement proper tenant isolation to prevent cross-workspace object manipulation
The use of repository.save() without distinguishing between create and update operations compounds this issue, as it implicitly allows overwrites when a matching primary key exists.
Attack Vector
The attack is network-based and requires low-privilege authenticated access to the Flowise application. An attacker must first authenticate to the system, then craft malicious requests to the DocumentStore creation endpoint.
The attack scenario involves the attacker specifying a target DocumentStore ID (either guessed, enumerated, or obtained through information disclosure) in their creation request. When the backend processes this request, it overwrites the existing DocumentStore object, effectively hijacking resources belonging to other workspaces or tenants.
The vulnerability is particularly impactful in multi-tenant environments where workspace isolation is a critical security requirement. For detailed technical information about the exploitation mechanism, refer to the GitHub Security Advisory.
Detection Methods for CVE-2026-41277
Indicators of Compromise
- Unexpected modifications to DocumentStore objects with altered ownership or workspace assignments
- API logs showing POST requests to DocumentStore endpoints with explicit id parameters
- Audit trail entries indicating DocumentStore updates that bypass normal edit workflows
- Cross-workspace data access anomalies in multi-tenant deployments
Detection Strategies
- Monitor API access logs for POST requests to /api/v1/document-store endpoints containing id fields in the request body
- Implement integrity monitoring for DocumentStore entity ownership and workspace association fields
- Deploy anomaly detection for authentication patterns followed by unusual DocumentStore creation activities
- Enable detailed audit logging for all DocumentStore CRUD operations
Monitoring Recommendations
- Configure alerting for DocumentStore modifications that change workspace or tenant associations
- Establish baseline behavior for DocumentStore creation patterns per authenticated user
- Monitor for enumeration attempts against DocumentStore endpoints
- Implement rate limiting and anomaly detection on the DocumentStore API endpoints
How to Mitigate CVE-2026-41277
Immediate Actions Required
- Upgrade Flowise to version 3.1.0 or later immediately
- Review DocumentStore audit logs for signs of exploitation or unauthorized modifications
- Verify integrity of existing DocumentStore objects in multi-tenant environments
- Implement additional network-level access controls to restrict API access while patching
Patch Information
The vulnerability has been addressed in Flowise version 3.1.0. Organizations should upgrade to this version or later to remediate the vulnerability. The fix implements proper input validation to prevent client-supplied primary keys from being used during entity creation, ensuring that create and update operations are properly separated with appropriate authorization checks.
For more information about the fix, consult the GitHub Security Advisory.
Workarounds
- Implement API gateway rules to strip or block id fields from incoming POST requests to DocumentStore endpoints
- Deploy a Web Application Firewall (WAF) rule to filter requests containing unexpected primary key specifications
- Restrict network access to Flowise instances to trusted users only until patching is complete
- Consider temporarily disabling DocumentStore creation functionality in high-risk multi-tenant environments
# Example: Upgrade Flowise to patched version
npm update flowise@3.1.0
# Or using yarn
yarn upgrade flowise@3.1.0
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
