CVE-2026-49143: Improper Control of Generation of Code ('Code Injection') in browserstack browserstack-runner
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.
AI Analysis
Technical Summary
CVE-2026-49143 is a remote code execution vulnerability in BrowserStack Runner (<=0.9.5) affecting the /_log HTTP handler. The handler processes user-supplied JSON data and passes it unsafely to Node.js's vm.runInNewContext() combined with eval(), allowing attackers to escape the sandbox via a host-context Function reference through util.format. This leads to full remote code execution on the underlying system without requiring authentication or user interaction.
Potential Impact
Successful exploitation results in full remote code execution on the host system running BrowserStack Runner, allowing attackers to execute arbitrary commands with the privileges of the application. This can lead to complete system compromise, data theft, or further network pivoting.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict network access to the /_log HTTP handler and monitor for suspicious activity. Avoid exposing BrowserStack Runner instances to untrusted networks.
CVE-2026-49143: Improper Control of Generation of Code ('Code Injection') in browserstack browserstack-runner
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.
CVSS v4.0
Score 8.7high
Affected software
pkg:npm/browserstack/browserstack-runnerRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-49143 is a remote code execution vulnerability in BrowserStack Runner (<=0.9.5) affecting the /_log HTTP handler. The handler processes user-supplied JSON data and passes it unsafely to Node.js's vm.runInNewContext() combined with eval(), allowing attackers to escape the sandbox via a host-context Function reference through util.format. This leads to full remote code execution on the underlying system without requiring authentication or user interaction.
Potential Impact
Successful exploitation results in full remote code execution on the host system running BrowserStack Runner, allowing attackers to execute arbitrary commands with the privileges of the application. This can lead to complete system compromise, data theft, or further network pivoting.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict network access to the /_log HTTP handler and monitor for suspicious activity. Avoid exposing BrowserStack Runner instances to untrusted networks.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-05-27T17:40:12.739Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a1f41c3e29bf47b5000d1a7
Added to database: 06/02/2026, 20:49:07 UTC
Last enriched: 07/15/2026, 10:07:24 UTC
Last updated: 07/31/2026, 19:22:59 UTC
Views: 110
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