Vulnerability · Published Jun 2, 2026 · Assigned by VulnCheck

CVE-2026-49143BrowserStack Runner 0.9.5 Unauthenticated RCE via /_log HTTP Handler

High 8.8

In plain English

A high-severity code injection in browserstack-runner from browserstack. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 57% of all known vulnerabilities).

Severity (CVSS 3.1)8.8High

Exploit odds (30 days)0.8%top 43.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	browserstack-runner	no fix listed	GHSA-6vr3-7wcx-v5g5

Affected products (as reported)

Vendor	Product	Versions
browserstack	browserstack-runner	0 – through 0.9.5

Weakness: CWE-94 · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

https://github.com/browserstack/browserstack-runner/security/advisories/GHSA-6vr3-7wcx-v5g5 vendor-advisory
https://www.vulncheck.com/advisories/browserstack-runner-unauthenticated-rce-via-log-http-handler third-party-advisory