CVE-2025-59434 is a critical vulnerability identified in the FlowiseAI Flowise product, specifically affecting the cloud-hosted version prior to the August 2025 patch. Flowise is a drag-and-drop interface designed to build customized large language model workflows. The vulnerability arises from an authenticated flaw in the Flowise Cloud platform, where users on the free tier can exploit the Custom JavaScript Function node to access sensitive environment variables belonging to other tenants. These environment variables include highly sensitive secrets such as OpenAI API keys, AWS credentials, Supabase tokens, and Google Cloud secrets. This results in a full cross-tenant data exposure, meaning that an attacker with legitimate access to a free-tier account can retrieve confidential information from other users, potentially leading to unauthorized access to cloud resources, data exfiltration, and further compromise. The vulnerability is classified under CWE-200 (Exposure of Sensitive Information) and CWE-284 (Improper Access Control), indicating that the root cause is insufficient access control mechanisms allowing unauthorized data exposure. The CVSS v3.1 base score is 9.6 (critical), with an attack vector of network (AV:N), low attack complexity (AC:L), requiring privileges (PR:L) but no user interaction (UI:N), and a scope change (S:C) indicating that the vulnerability affects resources beyond the initially compromised component. The impact on confidentiality and integrity is high, while availability is not affected. The issue was patched in the August 2025 Cloud-Hosted Flowise release, but prior versions remain vulnerable. No known exploits are reported in the wild as of the publication date.

For European organizations using FlowiseAI Flowise, especially those leveraging the cloud-hosted free tier, this vulnerability poses a significant risk. Exposure of environment variables containing API keys and cloud credentials can lead to unauthorized access to critical cloud infrastructure, data leakage, and potential lateral movement within the organization's cloud environment. This can result in data breaches involving personal data protected under GDPR, leading to regulatory penalties and reputational damage. Additionally, compromised API keys for services like OpenAI or Google Cloud could be abused to incur financial costs or manipulate AI-driven workflows, impacting business operations. The cross-tenant nature of the vulnerability means that even organizations with limited privileges on the platform could inadvertently expose their secrets to other tenants, increasing the attack surface. Given the critical severity and ease of exploitation by authenticated users without additional user interaction, the threat is substantial for any European entity using this service, particularly those in regulated sectors such as finance, healthcare, and government.

European organizations should immediately verify that their FlowiseAI Flowise cloud-hosted instances are updated to the August 2025 patched version or later. For those using the free tier, consider upgrading to paid tiers with stricter access controls or temporarily suspending use until the patch is applied. Implement strict credential management practices by rotating all exposed API keys and secrets that may have been compromised. Employ environment variable encryption and restrict access to sensitive configuration data within the platform. Monitor logs for unusual access patterns or data exfiltration attempts related to the Custom JavaScript Function node. Additionally, enforce multi-factor authentication and least privilege principles for all Flowise users to reduce the risk of unauthorized access. Organizations should also conduct internal audits to identify any potential misuse of exposed credentials and coordinate with FlowiseAI support for incident response guidance. Finally, consider isolating critical workflows from free-tier environments to minimize exposure.