CVE-2026-49143
CVE-2026-49143 is a Code Injection vulnerability in browserstack-runner. O3 Security confirms whether CVE-2026-49143 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
BrowserStack Runner 0.9.5 Unauthenticated RCE via /_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 CVE-2026-49143.
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.
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
BrowserStack Runner through 0.9.5 contains a remote code execution vulnerability in the /_log HTTP handler that allows unauthenticated network-adjacent attackers to execute arbitrary code by submitting crafted JSON request bodies to the handler, which passes user-supplied data to vm.runInNewContext() combined with eval(). Attackers can escape the Node.js vm sandbox by leveraging a host-context Function reference through util.format to access the host process via this.constructor.constructor, achieving full remote code execution on the underlying system without any authentication.
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 CVE-2026-49143 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 CVE-2026-49143 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 CVE-2026-49143. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-49143 in your dependencies?
O3 detects CVE-2026-49143 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.