Cline Kanban Server has a Cross-Origin WebSocket Hijacking Vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.6 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H

EPSS

• CVE-2026-44211: 0.18% estimated exploitation activity in the next 30 days; percentile 7.65 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The kanban npm package (used by the cline CLI) starts a WebSocket server on 127.0.0.1:3484 with no Origin header validation. Any website a developer visits can silently connect to the kanban server via WebSocket and: 1. Leak sensitive data in real-time: workspace filesystem paths, task titles/descriptions, git branch info, AI agent chat messages 2. Hijack running AI agent terminals by injecting arbitrary prompts into the agent's input, leading to remote code execution 3. Kill running agent tasks by terminating active sessions via the control WebSocket WebSocket connections are not subject to CORS restrictions. The browser sends them freely to localhost regardless of the page's origin. The kanban server accepts all connections without checking the Origin header. Affected Component - Package: kanban on npm (https://www.npmjs.com/package/kanban) - Repository: https://github.com/cline/kanban - Tested version: 0.1.59 - Installed via: cline CLI (cline --kanban or default cline…

Published by the source

8 May 2026, 20:43 UTC

Last modified by the source

9 Jun 2026, 11:00 UTC

Source last checked

26 Oct 2026, 12:53 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-5c57-rqjx-35g2

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-5c57-rqjx-35g2

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-5c57-rqjx-35g2

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# Patch Next advisory brief: CVE-2026-44211

Advisory: Cline Kanban Server has a Cross-Origin WebSocket Hijacking Vulnerability
IDs: CVE-2026-44211, GHSA-5c57-rqjx-35g2
Record: https://patchnext.com/advisories/cve-2026-44211 (revision 3, source checked 26 Oct 2026, 12:53 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm cline: affected <= 2.13.0

## Suggested inspection (read-only)
- `npm ls cline --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on cline.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5c57-rqjx-35g2 (GitHub-reviewed advisory GHSA-5c57-rqjx-35g2 lists affected ranges: npm cline >=0 <=2.13.0)
- Verified: https://osv.dev/vulnerability/GHSA-5c57-rqjx-35g2 (OSV record GHSA-5c57-rqjx-35g2 lists affected ranges: npm cline >=0 <=2.13.0)

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