## https://sploitus.com/exploit?id=E26D5E16-C41B-5153-A8A7-8438E159B569
# V8 Sandbox Escape PoC
> ⚠️ **CRITICAL SECURITY WARNING** ⚠️
> This repository contains a proof-of-concept for a potential V8 sandbox escape vulnerability. This is **PRIVATE RESEARCH** intended exclusively for responsible disclosure to Google VRP.
## ⛔ Disclaimer
**DO NOT:**
- Execute this PoC against production systems, services, or third-party infrastructure
- Redistribute or share this code publicly
- Test against products or services without explicit authorization
- Use for malicious purposes
This research is provided for vulnerability disclosure and defensive analysis only.
---
## Overview
This repository contains a proof-of-concept demonstrating a potential V8 sandbox escape vulnerability through corruption of WebAssembly internal metadata. The exploit uses APIs available exclusively in the `d8` shell with `--sandbox-testing` flag and ultimately constructs 64-bit memory read and write primitives within V8.
### Affected Component
- **Target:** V8 JavaScript engine, specifically WebAssembly and V8 sandbox
- **Environment:** `d8` shell with `--sandbox-testing` flag
- **Repository Commit Reference:** `1bb28860cbca49445756ca32ee188fdc4bd065df`
- **Status:** Under investigation by Google VRP
---
## Technical Details
### Vulnerability Summary
The PoC exploits WebAssembly table manipulation and internal V8 memory metadata to:
1. **Access internal structures** via `Sandbox.MemoryView` and helper functions
2. **Manipulate WebAssembly tables** using `TrustedDispatchTable` handles
3. **Trigger memory reuse** by forcing table growth and reclamation of freed entries
4. **Corrupt `CanonicalSig` representation** in reused WebAssembly entries
5. **Build 64-bit read/write primitives** (`read64`, `write64`) for arbitrary memory access
### Attack Flow
| Phase | Description |
|-------|-------------|
| **Setup** | Create memory views and helper functions using `Sandbox.getAddressOf` and `Sandbox.getObjectAt` |
| **Table Manipulation** | Read WebAssembly table internal fields and calculate handle offsets |
| **Memory Trigger** | Substitute a table handle and force growth to provoke use-after-free |
| **Reclamation** | Reclaim freed entries with compatible WebAssembly functions |
| **Exploitation** | Modify internal representations to build `read64`/`write64` primitives |
### Impact
If reproducible on an affected build, an attacker could:
- **Bypass sandbox guarantees** and read/write memory outside normal JavaScript/WebAssembly object boundaries
- **Corrupt memory structures** and modify trusted data
- **Escalate privileges** within the embedding process
- Potentially achieve **remote code execution** depending on additional mitigations
**Severity:** Depends on V8 version, mitigation effectiveness, and product context.
---
## Files
| File | Purpose |
|------|---------|
| `poc.js` | Main proof-of-concept exploit code (~2600 lines) |
| `Dockerfile` | Container setup for isolated testing environment |
| `SECURITY_REPORT.md` | Detailed security report (Spanish) |
| `SECURITY_REPORT.zip` | Compressed security documentation |
---
## Requirements
### For Testing (Controlled Environment)
- **Docker** (recommended for isolation)
- **V8 d8 binary** built with support for:
- `--sandbox-testing` flag
- WebAssembly (WASM) enabled
- Debug information
### Environment Setup
```bash
# Build container with d8
docker build --build-arg D8_TARBALL_URL="" -t v8-poc .
# Run in isolated environment
docker run --rm -v $(pwd):/work v8-poc
# Inside container: execute PoC
d8 --sandbox-testing /work/poc.js
```
---
## Responsible Disclosure
### Process
1. **Report submitted to:** Google Vulnerability Reward Program (VRP)
2. **Submission method:** Official Google VRP portal
3. **Artifacts:** Kept private during investigation
4. **Authorization:** Awaiting confirmation before public disclosure
### Required Information for Reproduction
When reporting or testing, provide:
- ✅ Exact V8/d8 version and operating system
- ✅ SHA-256 hash of test artifacts
- ✅ Console output and crash logs from disposable test environment
- ✅ Confirmation of successful read/write outside sandbox or crash
- ✅ Any mitigations or build flags that affect reproducibility
- ❌ NO production data, user secrets, or tests against live services
---
## Status
| Phase | Status |
|-------|--------|
| Static code analysis | ✅ Complete |
| Independent execution | ⏳ Pending |
| Affected version confirmation | ⏳ Pending |
| Google product impact confirmation | ⏳ Pending |
| CVE/upstream issue | ⏳ Pending |
---
## References
### Related V8 Components
- WebAssembly Table Management
- V8 Sandbox Implementation
- Internal Metadata Structures
- Memory Protection Mechanisms
### External Resources
- [V8 Project](https://v8.dev/)
- [Google VRP](https://www.google.com/about/appsecurity/reward-program/)
- [WebAssembly Specification](https://webassembly.org/)
---
## Contributors
- **Researcher:** nek-3231
- **Status:** Active investigation
---
## License
This repository does not include a license. Use is restricted to authorized security research and responsible disclosure to Google.
---
## Contact & Reporting
**For Google VRP team:**
- Use official Google VRP portal for submission
- Keep all artifacts private
- Allow time for investigation and response
**For security researchers:**
- Do NOT fork, clone, or distribute publicly
- Do NOT test against any systems without explicit authorization
- Coordinate with Google VRP if you have related findings
---
**Last Updated:** 2026-08-24
**Sensitivity:** 🔒 CONFIDENTIAL - SECURITY RESEARCH