Active Exploitation of Flowise CustomMCP RCE Exposes Thousands of Internet-Facing Instances
Threat actors are actively exploiting CVE-2025-59528, a CVSS 10.0 remote code execution flaw in the open-source AI platform Flowise. The bug affects Flowise versions through 3.0.5 and stems from the CustomMCP node unsafely passing user-controlled input into JavaScript execution, allowing attackers with an API token to run arbitrary code with full Node.js runtime privileges. Researchers said the issue can be triggered remotely via a crafted HTTP POST request without user interaction, leading to operating system command execution, filesystem access, sensitive data theft, and full system compromise.
Security researchers observed in-the-wild exploitation originating from a single Starlink IP address, while warning that roughly 12,000 to 15,000 internet-exposed Flowise instances sharply expand the attack surface for opportunistic attacks. Flowise disclosed the vulnerability in 2025, credited researcher Kim SooHyun, and patched the flaw in version 3.0.6. The incident marks the third Flowise vulnerability reported as exploited in the wild after CVE-2025-8943 and CVE-2025-26319, increasing pressure on organizations to upgrade immediately and limit public exposure of Flowise APIs.
Get ahead of threats like this
Mallory correlates global threat intelligence with your attack surface — know if you’re exposed before adversaries strike.
How this story unfolded
6 events from the most recent confirmed update back to the earliest known activity.
OX Security discloses broader MCP design flaw impacting Flowise and AI tools
OX Security disclosed a critical remote command execution exposure tied to architectural flaws in Anthropic's MCP SDKs, affecting Flowise and multiple other AI frameworks rather than a single-product bug. The researchers reported successful command execution on six production platforms, identified several exploitation families, and said at least ten CVEs had been issued across affected products.
VulnCheck flags two more Flowise flaws under active exploitation
VulnCheck reported that two additional critical Flowise vulnerabilities, CVE-2025-8943 and CVE-2025-26319, were also being actively exploited. The company said it was providing customers with exploitation data and defensive artifacts including a PCAP, YARA rule, network signatures, and a target Docker container.
Researchers warn 12,000-15,000 internet-exposed Flowise instances are at risk
Security reporting highlighted that roughly 12,000 to 15,000 Flowise instances were exposed to the public internet, increasing the likelihood of opportunistic attacks. The exposure amplified the impact of the actively exploited RCE flaw.
VulnCheck observes in-the-wild exploitation of CVE-2025-59528
In April 2026, VulnCheck reported active exploitation of CVE-2025-59528 against Flowise instances. The observed activity was initially traced to a single Starlink IP address.
Flowise fixes CVE-2025-59528 in version 3.0.6
Flowise released a fix for CVE-2025-59528 in npm package version 3.0.6. The vulnerability affects versions up to 3.0.5 and can enable remote code execution through unsafe execution of user-supplied JavaScript.
Flowise discloses CVE-2025-59528 and credits researcher Kim SooHyun
Flowise disclosed CVE-2025-59528, a maximum-severity code injection flaw in the CustomMCP node, in September 2025. The issue was credited to researcher Kim SooHyun.
Related entities
Vulnerabilities, threat actors, malware, products, organizations, and breaches Mallory has linked to this story.
Sources
10 references tracked. Mallory keeps watching after this page renders.
Critical Vulnerability In Flowise Allows Remote Command Execution Via MCP Adapters
cybersecuritynews.com
Open sourceFlowise RCE Vulnerability CVE-2025-59528 Exploited Now
thecyberexpress.com
Open sourceHackers exploit a critical Flowise flaw affecting thousands of AI workflows | CSO Online
csoonline.com
Open sourceActive exploitation of max severity Flowise bug threatens broad compromise | brief | SC Media
scworld.com
Open sourceFlowise AI Agent Builder Under Active CVSS 10.0 RCE Exploitation; 12,000+ Instances Exposed
thehackernews.com
Open sourceCVE-2025-59528: Flowise CustomMCP Code Injection RCE - TheCyberThrone
thecyberthrone.in
Open sourceMax severity Flowise RCE vulnerability now exploited in attacks
bleepingcomputer.com
Open sourceRCE in FlowiseAI/Flowise · Advisory · FlowiseAI/Flowise · GitHub
github.com
Open sourceSee the full picture, correlated to your attack surface.
Map indicators from this story to your assets and identify affected systems in minutes.
Every observed campaign, victim, and pivot linked to actors named in this story.
Malware, exploits, and IOCs connected to the activity described here.
YARA, Sigma, and Snort rules deployed to your SIEM as soon as they’re published.
Get matching new stories delivered to your team as they break — not the next morning.
Ask questions about this story and take action on the answers.
Related stories
Other stories Mallory is tracking that overlap on entities, sources, or topic labels.
Flowise Custom MCP Flaw Enables One-Click Remote Code Execution
Researchers disclosed **CVE-2026-40933**, a critical remote code execution flaw in self-hosted **Flowise** deployments tied to the platform’s Custom **MCP** support over `stdio`. The issue lets an authenticated attacker execute arbitrary OS commands with the privileges of the Flowise process by supplying a malicious MCP server configuration, either directly or by embedding it in a shared chatflow. In the demonstrated one-click scenario, importing the crafted chatflow alone can trigger server-side command execution when Flowise enumerates available MCP actions, before any save or run step. **Flowise Cloud** is not affected because `stdio` MCP is disabled, but open-source and enterprise self-hosted deployments are vulnerable by default. Reporting on the flaw said Flowise’s initial mitigation—blocking risky flags for allowlisted commands—does not fix the underlying problem because the feature still launches user-controlled processes, and researchers showed it can be bypassed through environment variables. Recommended defenses include upgrading to **Flowise 3.1.0**, limiting who can add or import MCP configurations, isolating Flowise from sensitive internal systems, and disabling `stdio` MCP unless it is strictly required by setting: ```bash CUSTOM_MCP_PROTOCOL=sse ``` The disclosures also warn that the bug reflects a broader architectural and supply-chain risk for agentic AI platforms that expose unsandboxed `stdio`-based MCP configuration to lower-trust users or untrusted artifacts.
Jun 1, 2026
Critical Flowise RCE Vulnerability CVE-2025-61913 Enables Arbitrary File Read and Write
A critical remote code execution vulnerability, tracked as CVE-2025-61913, has been identified in Flowise, a drag-and-drop user interface for building customized large language model flows. The flaw exists in versions prior to 3.0.8 and is caused by insufficient restrictions in the WriteFileTool and ReadFileTool components, which fail to properly validate file path access. This oversight allows authenticated attackers to read and write arbitrary files to any location on the file system, significantly increasing the risk of remote code execution. The vulnerability has been assigned a CVSS score of 10.0, indicating its maximum severity and potential for exploitation. According to security advisories, the issue can be exploited remotely, making it a high-priority concern for organizations using affected versions of Flowise. The vulnerability was publicly disclosed on October 8, 2025, and a security update was released in version 3.0.8 to address the issue. Attackers leveraging this flaw could gain unauthorized access to sensitive files, modify system configurations, or deploy malicious payloads, potentially leading to full system compromise. The vulnerability affects all installations of Flowise prior to the patched version, though the exact list of affected products and vendors has not been fully enumerated. Security researchers emphasize the critical nature of the flaw due to the ease of exploitation and the broad impact on confidentiality, integrity, and availability. Organizations are strongly advised to upgrade to Flowise version 3.0.8 or later to mitigate the risk. The vulnerability was reported through GitHub security advisories, highlighting the importance of monitoring open-source project disclosures. No evidence of active exploitation in the wild has been reported as of the disclosure date, but the public availability of technical details increases the urgency for remediation. The flaw underscores the risks associated with insufficient input validation in file handling components of web applications. Security teams should review their deployment of Flowise and apply the necessary patches without delay. In addition to patching, organizations should audit access logs for signs of suspicious file operations that could indicate attempted exploitation. The incident serves as a reminder of the critical need for secure coding practices and regular vulnerability assessments in software development.
Mar 21, 2026
Flowise fixes multiple flaws enabling RCE, tenant abuse, and API credit theft
Flowise disclosed and fixed a cluster of high-severity vulnerabilities in versions prior to **3.1.0**, including multiple paths to remote code execution. The most serious issues affect the platform's CSV and Airtable agent components, where unsanitized user input or LLM-generated Python code could be evaluated without proper sandboxing. Advisories for **`CVE-2026-41137`**, **`CVE-2026-41264`**, **`CVE-2026-41138`**, and **`CVE-2026-41265`** describe authenticated and unauthenticated attack paths that let attackers inject malicious payloads through chatflows or agent inputs and execute code on the Flowise server, with potential impact to confidentiality, integrity, and availability. Flowise **3.1.0** also addresses non-RCE flaws that could expose multi-tenant environments and consume third-party service credits. **`CVE-2026-41279`** affects the unauthenticated text-to-speech endpoint at **`POST /api/v1/text-to-speech/generate`**, which could accept an arbitrary **`credentialId`** and use decrypted stored credentials such as OpenAI or ElevenLabs API keys to generate speech, enabling API credit abuse. In **Flowise Cloud**, **`CVE-2026-41267`** allows improper mass assignment during account registration, letting unauthenticated attackers inject server-managed fields and manipulate organization associations, ownership metadata, timestamps, and role mappings across tenants. Organizations running Flowise or Flowise Cloud should upgrade to **3.1.0** and review exposed chatflows, stored credentials, and tenant registration controls.
May 4, 2026