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
BrowserStack Runner through version 0.9.5 contains a remote code execution vulnerability in its /_log HTTP handler. The handler processes user-supplied JSON request bodies and passes them to vm.runInNewContext() combined with eval(), enabling attackers to escape the Node.js sandbox. By leveraging a host-context Function reference through util.format, attackers can access the host process via this.constructor.constructor, resulting in full remote code execution on the underlying system without authentication. The vulnerability has a CVSS 4.0 score of 8.7, indicating high severity.
Potential Impact
Successful exploitation allows unauthenticated, network-adjacent attackers to execute arbitrary code on the host running BrowserStack Runner, potentially leading to full system compromise. This can result in unauthorized control over the affected system and any data or processes it manages.
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 to trusted users only, and consider disabling or isolating the BrowserStack Runner service to reduce exposure.
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
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
BrowserStack Runner through version 0.9.5 contains a remote code execution vulnerability in its /_log HTTP handler. The handler processes user-supplied JSON request bodies and passes them to vm.runInNewContext() combined with eval(), enabling attackers to escape the Node.js sandbox. By leveraging a host-context Function reference through util.format, attackers can access the host process via this.constructor.constructor, resulting in full remote code execution on the underlying system without authentication. The vulnerability has a CVSS 4.0 score of 8.7, indicating high severity.
Potential Impact
Successful exploitation allows unauthenticated, network-adjacent attackers to execute arbitrary code on the host running BrowserStack Runner, potentially leading to full system compromise. This can result in unauthorized control over the affected system and any data or processes it manages.
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 to trusted users only, and consider disabling or isolating the BrowserStack Runner service to reduce exposure.
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: 6/2/2026, 8:49:07 PM
Last enriched: 6/2/2026, 9:03:41 PM
Last updated: 6/2/2026, 10:49:11 PM
Views: 5
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.