External risk intelligence

Cline Cross-Origin WebSocket Hijack Vulnerability

CVE advisorySeverity: CRITICAL (CVSS 9.6)

CVE-2026-44211

Cline is an IDE extension and coding assistant tool designed for local developer environments. Kanban servers used in this context are typically run locally or within private development environments, not as public-facing internet services.

Missing Authentication

Cline

2.13.0 and earlier

Halo Surface Signal: 1 out of 5 — much less likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

A critical vulnerability in Cline, an AI-powered coding assistant, could allow unauthorized access to connected systems. This issue affects how Cline's Kanban servers handle certain network communications, potentially enabling attackers to hijack connections. While the full business impact is unclear, the severity indicates a need to understand if and how Cline is used within the organization.

Cross-origin hijack in coding assistant.
Critical flaw impacts connected systems.
Confirm if Cline is in use.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this by tricking a user into interacting with a malicious website. This malicious site would then attempt to hijack the WebSocket connection used by the Cline Kanban server, potentially leading to unauthorized access and control of the user's development environment. The exact method for achieving this hijacking without further context is uncertain.

Requires user interaction with a malicious site.
Hijacks WebSocket connection to Kanban server.
Risk of unauthorized access and control.

Live Threat

Current exploitation, exposure, and threat context

This vulnerability could allow an attacker to hijack WebSocket connections to Cline Kanban servers, potentially leading to the exposure or modification of sensitive information. This risk exists when a user interacts with a malicious server while using a supported Cline product.

Compromised user session data.
Cross-origin communication interception.
Unauthorized access to system functions.

Operational Fix

Recommended remediation, mitigation, and detection steps

The affected technology, Cline, is primarily a developer tool. Ownership likely resides with development teams or platform engineering, depending on how Cline is deployed and managed. The initial focus should be on identifying all instances of Cline Kanban servers within the development and CI/CD environments, assessing their reachability, and understanding their criticality to business operations. Coordinating with the vendor for a patch or workaround is essential, especially given the current lack of a public fix.

Development or Platform Engineering teams own the issue.
Verify server reachability and business criticality.
Coordinate with the vendor for a solution.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

Free EASM Trial See How Signal Works

Frequently asked questions

What is Cline and how is it used?

Cline is an autonomous coding agent that functions as an IDE extension, SDK, or command-line tool. Developers use it to assist with programming tasks, manage project workflows, and interact with codebases directly within their development environment. Its Kanban server component helps organize these tasks, effectively acting as an interface between the user's workspace and the coding assistant's operational logic.

What does this CVE mean in plain English?

This vulnerability, classified as CWE-306 (Missing Authentication for Critical Function) and CWE-1385 (Missing Origin Validation in WebSockets), describes a flaw where the Cline Kanban server fails to properly verify the source of a connection. Essentially, an unauthorized website can send commands to the server as if it were the legitimate user, allowing an attacker to intercept or control the communication session.

How can an attacker trigger this vulnerability?

The attack requires the user to interact with a malicious website while their Cline Kanban server is running. If the user visits a site designed to exploit this, the browser can initiate a connection to the local server without proper authorization. Simply having the server installed is not enough; the vulnerability does not trigger if the user avoids interacting with untrusted websites or external links while the development environment is active.

Do I need to worry about internet exposure?

According to Halo Surface Signal, this risk is very unlikely because Cline is a local developer tool. Kanban servers are generally restricted to private development environments rather than being exposed to the public internet. However, you should still evaluate if your specific configuration inadvertently allows remote access to these local services, as that would change the risk profile from local to network-accessible.

When should I take action for CVE-2026-44211?

Since there is currently no vendor patch, your priority is identification. First, inventory where Cline is deployed across your development and CI/CD environments. Determine which teams are responsible for these instances and ensure they are aware of the risk. Because the tool often runs in local developer workspaces, focus on internal communication rather than broad network changes while you monitor the vendor's security channels for a future update.

References

github.com/cline/cline/security/advisories/GHSA-5c57-rqjx-35g2

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.