CVE-2026-25586
📋 TL;DR
This CVE describes a sandbox escape vulnerability in SandboxJS library versions before 0.8.29. Attackers can bypass JavaScript sandboxing by shadowing the hasOwnProperty method, allowing access to blocked prototype properties like __proto__. This enables Object.prototype pollution and persistent cross-sandbox impact, affecting any application using vulnerable SandboxJS versions for JavaScript isolation.
💻 Affected Systems
- SandboxJS
⚠️ Risk & Real-World Impact
Worst Case
Complete sandbox escape allowing arbitrary code execution on the host system, privilege escalation, and persistent compromise of the application environment.
Likely Case
Sandbox bypass enabling access to sensitive data, modification of application behavior, and potential lateral movement within the application context.
If Mitigated
Limited impact if sandboxed code has minimal privileges and access to sensitive resources is properly restricted.
🎯 Exploit Status
Exploitation requires the ability to execute JavaScript within the sandbox, but once inside, the escape is straightforward.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.8.29
Vendor Advisory: https://github.com/nyariv/SandboxJS/security/advisories/GHSA-jjpw-65fv-8g48
Restart Required: Yes
Instructions:
1. Update SandboxJS dependency to version 0.8.29 or later. 2. Update package.json to specify 'sandboxjs': '>=0.8.29'. 3. Run npm update or yarn update. 4. Restart the application.
🔧 Temporary Workarounds
Disable SandboxJS Usage
allTemporarily disable or remove SandboxJS functionality until patched
Input Validation
allImplement strict input validation and sanitization for any JavaScript code passed to SandboxJS
🧯 If You Can't Patch
- Isolate the application using SandboxJS in a container or VM with minimal privileges
- Implement network segmentation to limit potential lateral movement from compromised systems
🔍 How to Verify
Check if Vulnerable:
Check package.json or node_modules for SandboxJS version. If version is less than 0.8.29, the system is vulnerable.Check Version:
npm list sandboxjs | grep sandboxjsVerify Fix Applied:
Verify SandboxJS version is 0.8.29 or higher in package.json and node_modules/sandboxjs/package.json📡 Detection & Monitoring
Log Indicators:
- Unusual JavaScript execution patterns
- Attempts to access __proto__ or prototype properties
- Sandbox escape attempts in application logs
Network Indicators:
- Unexpected outbound connections from sandboxed code
- Unusual data exfiltration patterns
SIEM Query:
source=application_logs AND ("__proto__" OR "hasOwnProperty" OR "sandbox escape")