Cline Hub Dashboard WebSocket Origin Validation Vulnerability
Cline is an autonomous coding agent as an SDK, IDE extension, or CLI assistant. Prior to 3.0.30, the Cline Hub dashboard server launched by the cline dashboard command accepts WebSocket connections on the /browser endpoint without validating the Origin header, and when ROOM_SECRET is unset for local 127.0.0.1 binds, isAuthorizedBrowserRequest() allows attacker-controlled websites to send desktopCommand frames that read workspace state, mutate MCP and provider settings, and trigger command execution when a provider or model is configured. This issue is fixed in version 3.0.30.
Quick answer
Cline should be reviewed and updated if it matches the affected versions. The recommended fix is to apply the vendor-supported patched version or the mitigation steps below, then retest the public website with Fixnx.
Who is affected
Affected versions
- Cline prior to 3.0.30
Fixed versions
- 3.0.30
How to fix it
Cline before 3.0.30 exposed a Hub dashboard WebSocket origin-validation flaw that could let a malicious page mutate MCP or provider settings when the local dashboard is reachable. Update Cline, set a room secret, and review tool/provider settings for command execution risk.
- Inventory developer workstations and automation hosts running Cline before 3.0.30.
- Update Cline to 3.0.30 or later.
- Set ROOM_SECRET or the vendor-recommended equivalent so local dashboard sessions require a secret.
- Bind local dashboard services to localhost only and block access from untrusted networks.
- Review Cline MCP server settings, provider settings, model keys, and tool permissions for unauthorized changes.
- Rotate API keys, model provider tokens, repository credentials, and MCP secrets if settings may have been modified.
- Educate developers not to browse untrusted pages while sensitive local automation dashboards are running.
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Verify the fix
- Confirm Cline reports version 3.0.30 or later.
- Validate WebSocket connections from untrusted origins are rejected.
- Confirm dashboard access requires the configured secret where applicable.
- Review Cline configuration history and MCP logs for unexpected changes or command execution.
- Run a Fixnx scan and confirm no local dashboard port is exposed publicly.
Related categories
Trusted references
FAQ
What is affected by CVE-2026-59723?
Cline versions listed as affected should be reviewed: Cline prior to 3.0.30.
What should I fix first?
Start with internet-facing sites, admin panels, login flows, plugins, themes, modules, packages, and systems that process user-controlled input or sensitive data.
How do I confirm the fix worked?
Apply the patched version or mitigation, clear caches where relevant, retest the affected workflow, and run a new Fixnx scan to verify public website exposure signals.
Why can this risk appear in multiple categories?
A vulnerability can belong to more than one platform or ecosystem. Fixnx keeps one canonical risk page while also listing it in every relevant category.