External risk intelligence

Flowise Authentication Bypass via Weak Default JWT Secrets

CVE advisorySeverity: CRITICAL (CVSS 9.3)

CVE-2026-56271

Flowise is a web-based low-code platform for building LLM applications. These applications are commonly deployed as internet-facing web services or APIs to allow external users or systems to interact with the LLM workflows, making the authentication middleware reachable from the public internet in typical deployment patterns.

Authentication Bypass

Flowiseai Flowise

before 3.1.0

Halo Surface Signal: 4 out of 5 — likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory concerns a vulnerability in Flowise's authentication system that could allow unauthorized access. The issue stems from weak, hardcoded default security credentials that are used if not explicitly configured by the user. An attacker could potentially exploit this to bypass authentication and gain access to the system, including administrative functions.

Weak default credentials allow unauthorized access.
Critical systems could be compromised via authentication bypass.
Confirm if default credentials are in use.

Attack Path

How an attacker could exploit the issue

An attacker can exploit this vulnerability by sending unauthenticated requests to the Flowise application. If the application is configured with default JWT secrets and audience/issuer values, an attacker can craft a malicious JSON Web Token (JWT) to impersonate any user, including administrators, thereby bypassing authentication and gaining unauthorized access.

No special access needed.
Forge JWTs using default secrets.
Impersonate any user, bypass authentication.

Live Threat

Current exploitation, exposure, and threat context

The authentication middleware in Flowise could be bypassed when default JWT secrets and values are used. This may allow an attacker to impersonate users, including administrators, when the application falls back to these known defaults, potentially impacting service integrity.

User and administrator access to the system.
Unauthenticated access to application features.
Unauthorized user impersonation.

Operational Fix

Recommended remediation, mitigation, and detection steps

This advisory impacts Flowise deployments that have not explicitly configured environment variables for JWT secrets and audience/issuer values. Application owners and platform teams are primarily responsible for securing these configurations. The immediate first step is to identify all Flowise instances, assess their exposure and business criticality, and determine the accountable owner for remediation planning.

Application owners must verify JWT configurations.
Confirm external reachability and business criticality.
Plan remediation based on identified risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

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Frequently asked questions

What is Flowise and why is it used?

Flowise is a low-code platform designed for building and managing applications powered by Large Language Models (LLMs). It allows users to visually construct workflows that connect LLMs to various data sources or tools. Because these workflows often act as services or APIs, Flowise is frequently deployed as a web application to enable external systems or users to interact with the underlying AI models.

What does CWE-321 mean for CVE-2026-56271?

CWE-321 refers to the use of hardcoded, cryptographic keys. In CVE-2026-56271, Flowise relies on publicly known default values for its JWT authentication tokens if the administrator fails to set specific environment variables. Because these secret keys, audience, and issuer values are embedded in the software's code, an attacker can use them to generate their own valid authentication tokens, effectively bypassing the security checks meant to protect the system.

How can an attacker trigger this authentication bypass?

An attacker can trigger this vulnerability by sending unauthenticated requests to a Flowise instance that uses the default settings. If the required environment variables for JWT security are missing, the application automatically reverts to the insecure, hardcoded defaults. The vulnerability is not triggered if an administrator has properly configured the instance with unique, custom environment variables for these JWT parameters, as the hardcoded values are then bypassed.

Why should I care about this if my instance is internal?

Halo Surface Signal indicates that Flowise instances are typically deployed as internet-facing web services, meaning many are directly reachable from the public internet. While internal-only deployments reduce the immediate risk from external actors, any system reachable by others on your network remains at risk. You should evaluate your instance's reachability to determine how easily an unauthorized party could reach the authentication middleware.

How do I secure my Flowise installation?

The most important first step is to verify that you have explicitly set the environment variables for JWT_AUTH_TOKEN_SECRET, JWT_REFRESH_TOKEN_SECRET, JWT_AUDIENCE, and JWT_ISSUER. Check your current server configuration to ensure these are not relying on the software's default values. Once you have identified all your Flowise instances, prioritize those that are internet-facing to ensure they are using unique, secure credentials that prevent unauthorized user impersonation.

References

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.