CVE-2026-64651 AI SDK OpenCode Harness Tool Relay Authorization Bypass
Untrusted sandbox code can bypass authorization to invoke host tools, enabling secret access and cloud operations in AI SDK harness environments.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-64651?
CVE-2026-64651 is a medium-severity authentication bypass vulnerability in vercel @ai-sdk/harness-opencode, published on 20 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
The `@ai-sdk/harness-opencode` tool connects HarnessAgent to OpenCode through a sandboxed bridge. Prior to version 1.0.28, the tool relay authorizes requests from any process whose command line contains an allowed helper script path (`host-tool-mcp.mjs`). This allows untrusted code executing in the sandbox to invoke arbitrary host-exposed tools including secret lookups, deployment operations, and cloud API calls without a corresponding model-authorized tool-call event. Exploitation requires a Linux environment (the vulnerable fallback checks `process.platform === 'linux'` and reads `/proc`); an active harness session with one or more host-provided tools; and untrusted code executing in the sandbox (e.g. a malicious dependency, build script, or lifecycle hook) The fix in version 1.0.28 removes the process-path authorization fallback entirely. Relay requests are now only accepted after exact, short-lived, one-time authorization matching the tool name and input from a bridge-observed model event. Some workarounds are available. Do not run the OpenCode harness on untrusted repositories or with untrusted dependencies, and/or limit host-exposed tools to non-sensitive operations when working with untrusted code.
Weakness: CWE-863
Which versions are affected by CVE-2026-64651?
How do I fix CVE-2026-64651?
No fix has been published for CVE-2026-64651 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-64651 being exploited?
There is no known exploitation of CVE-2026-64651 in the wild and no public exploit code.
Sources
Also known as GHSA-g48p-5rr5-8rgq.