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Description

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.

PUBLISHED Reserved 2026-05-27 | Published 2026-06-02 | Updated 2026-06-03 | Assigner VulnCheck




HIGH: 8.7CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

HIGH: 8.8CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem types

Improper Control of Generation of Code ('Code Injection')

Product status

Default status
affected

Any version
affected

Credits

Christ Bouchuen finder

References

github.com/...runner/security/advisories/GHSA-6vr3-7wcx-v5g5 exploit

github.com/...runner/security/advisories/GHSA-6vr3-7wcx-v5g5 vendor-advisory

www.vulncheck.com/...nauthenticated-rce-via-log-http-handler third-party-advisory

cve.org (CVE-2026-49143)

nvd.nist.gov (CVE-2026-49143)

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