CVE-2026-59723: Cline Hub dashboard cross-origin WebSocket hijacking (< 3.0.30)
- Product
- cline (npm)
- CVE
- CVE-2026-59723
- Affected
- < 3.0.30
- Fixed in
- 3.0.30
Last verified against sources: October 16, 2026
Am I affected?
cline (npm): affected < 3.0.30. Fixed in 3.0.30.
What to do now
- Upgrade cline to 3.0.30 or later. [1]
General practice, not from the source: if the affected software could read tokens or credentials, rotate them after upgrading; pin versions and review changes before updating tools your agents run.
What happened
- According to GitHub Advisory Database's advisory (Sept 24, 2026), the Cline Hub dashboard server accepted WebSocket connections on /browser without validating the Origin header and started without a room secret by default on 127.0.0.1. [1]
Impact
- A website visited by a developer could open a WebSocket to ws://127.0.0.1:8787/browser, inject a malicious stdio MCP server entry via upsert_mcp_server, and trigger command execution (CVSS 8.8). [1]
What was done
- Fixed in cline 3.0.30. [1]
Sources
- GHSA-3cj3-hqcr-g934 — GitHub Advisory Database
Every statement above was checked against these sources before publishing. Spotted an error? Tell us and we will correct it with a dated note.
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[CVE-2026-59723] CVE-2026-59723: Cline Hub dashboard cross-origin WebSocket hijacking (< 3.0.30)
Product: cline (npm) | Affected: < 3.0.30 | Fixed in: 3.0.30
Summary: According to GitHub Advisory Database's advisory (Sept 24, 2026), the Cline Hub dashboard server accepted WebSocket connections on /browser without validating the Origin header and started without a room secret by default on 127.0.0.1.
Source & remediation on AgentArmorHQ: https://agentarmorhq.com/incidents/2026/09/cve-2026-59723-cline-hub-websocket-hijackingCorrections
Report an error or request a correction. We review requests within 5 business days and add a dated correction note.
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