RCE in Browserstack Browserstack-Runner
CVE-2026-49143
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.
Vulnerability class: RCE (Remote Code Execution)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.007 (50.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.007 · change: +0.003
Affected products
- Browserstack Browserstack-Runner — versions 0
Weakness classification (CWE)
References
- github.com/browserstack/browserstack-runner/security/advisories/GHSA-6vr3-7wcx-… (vendor-advisory)
- www.vulncheck.com/advisories/browserstack-runner-unauthenticated-rce-via-log-ht… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-49143?
- CVE-2026-49143 is a high-severity vulnerability in Browserstack Browserstack-Runner, classified under Code Injection. CVSS score: 8.8/10. Published 2026-06-02.
- How severe is CVE-2026-49143?
- High severity. CVSS v3 base score is 8.8 out of 10.