# Writing N-day Exploit PoCs from Vendor Patch Diff Analysis Using patch-diff-exploit

> Automate N-day exploit PoC creation. Learn how to convert vendor patches into working exploits using patch-diff-exploit from the reverse-skill repository. Master vulnerability analysis.

- Repository: [ZhaoXu/reverse-skill](https://github.com/zhaoxuya520/reverse-skill)
- Tags: how-to-guide
- Published: 2026-08-09

---

**The reverse-skill repository provides a platform-agnostic routing framework that automates the workflow for converting vendor security patches into working proof-of-concept exploits through its patch-diff-exploit skill module.**

Generating reliable proof-of-concept exploits for N-day vulnerabilities requires systematic analysis of vendor patch diffs to identify the exact vulnerability class and affected code paths. The `zhaoxuya520/reverse-skill` repository implements a structured routing architecture that guides security analysts through writing N-day exploit PoCs from vendor patch diff analysis using the `patch-diff-exploit` skill. This approach transforms manual binary diffing procedures into a reproducible, auditable workflow integrated with automated tool management.

## Understanding the reverse-skill Routing Architecture

The foundation of the N-day exploit generation process relies on a centralized routing system defined in [`skills/config/routing.json`](https://github.com/zhaoxuya520/reverse-skill/blob/main/skills/config/routing.json). This JSON file serves as the single source of truth that maps task keywords to specific skill modules.

The routing hierarchy begins with [`skills/SKILL.md`](https://github.com/zhaoxuya520/reverse-skill/blob/main/skills/SKILL.md), which acts as the master entry point for all security workflows. When an analyst initiates a task, the system consults [`skills/routing.md`](https://github.com/zhaoxuya520/reverse-skill/blob/main/skills/routing.md) to match keywords like "N-day" or "patch diff" against available capabilities. This matrix-based approach ensures that requests for patch diff analysis are automatically directed to the appropriate skill directory, as documented in [`docs/ARCHITECTURE.md`](https://github.com/zhaoxuya520/reverse-skill/blob/main/docs/ARCHITECTURE.md).

## How the patch-diff-exploit Skill Works

Located at [`skills/patch-diff-exploit/SKILL.md`](https://github.com/zhaoxuya520/reverse-skill/blob/main/skills/patch-diff-exploit/SKILL.md), this module defines a five-step methodology for transforming patch differences into exploitable code:

1. **Acquire Target Binaries** – Download before-and-after patch binaries (MSU/MSP packages for Windows, `.deb` or `.rpm` files for Linux distributions).

2. **Symbol Alignment** – Migrate debug symbols using PDB files or binary-diff techniques to establish accurate function mapping between versions.

3. **Differential Analysis** – Execute binary diffing tools such as BinDiff, ghidriff, or Diaphora to identify code changes.

4. **Vulnerability Identification** – Filter functions with similarity scores between **0.5 and 0.95**, focusing on newly added security checks that indicate patched vulnerabilities.

5. **PoC Development** – Write targeted proof-of-concept code exploiting the identified bug class.

The skill documentation includes ready-made bootstrap commands for installing missing dependencies. For example, analysts can install `ghidriff` via pip when the tool is not present on the system.

## Automating Tool Discovery and Bootstrap

Before executing the patch-diff-exploit workflow, the repository ensures all required utilities are available through automated detection scripts. The `skills/scripts/refresh-tool-index.ps1` (Windows) and [`skills/scripts/refresh-tool-index.sh`](https://github.com/zhaoxuya520/reverse-skill/blob/main/skills/scripts/refresh-tool-index.sh) (Linux/macOS) scripts scan the environment and generate [`tool-index.md`](https://github.com/zhaoxuya520/reverse-skill/blob/main/tool-index.md), cataloging available reverse engineering tools.

When dependencies are missing, `skills/scripts/bootstrap-reverse.ps1` (or its Linux equivalent) references [`bootstrap-manifest.json`](https://github.com/zhaoxuya520/reverse-skill/blob/main/bootstrap-manifest.json) to perform automatic installation. This bootstrap layer eliminates manual configuration errors and ensures consistent tool availability across different analysis environments.

## Executing the N-day Exploit Workflow

To initiate the patch-diff-exploit process, analysts invoke the master routing script with contextual hints:

```bash
git clone https://github.com/zhaoxuya520/reverse-skill.git
cd reverse-skill

# Refresh tool index

powershell -File skills/scripts/refresh-tool-index.ps1

# Linux alternative: bash skills/scripts/refresh-tool-index.sh

```

Once the environment is prepared, execute the primary route:

```powershell
powershell -NoProfile -ExecutionPolicy Bypass -File skills/scripts/master-route.ps1 -Hint "N-day exploit from Windows patch"

```

The `master-route.ps1` script parses [`skills/config/routing.json`](https://github.com/zhaoxuya520/reverse-skill/blob/main/skills/config/routing.json), matches the hint keywords against the routing matrix, and automatically navigates to the `patch-diff-exploit` skill directory. This automation reduces the cognitive overhead of manually locating the correct workflow documentation.

## Downstream Exploit Development

After generating a working PoC through the patch-diff-exploit skill, the routing matrix documented in the skill's **routing context** section facilitates automatic hand-off to specialized downstream modules. The system forwards successful cases to `pwn-chain` for full exploit development and weaponization, or to `pentest-tools/network-attack-defense` for network-based attack scenarios.

This integration ensures that N-day analysis seamlessly transitions into comprehensive exploit chains without requiring manual reconfiguration of the analysis environment.

## Summary

- The `reverse-skill` repository uses [`skills/config/routing.json`](https://github.com/zhaoxuya520/reverse-skill/blob/main/skills/config/routing.json) as a centralized routing mechanism to direct N-day exploit tasks to the appropriate skill modules.
- The `patch-diff-exploit` skill at [`skills/patch-diff-exploit/SKILL.md`](https://github.com/zhaoxuya520/reverse-skill/blob/main/skills/patch-diff-exploit/SKILL.md) provides a five-step framework for converting vendor patches into PoCs through binary diffing and vulnerability identification.
- Automated scripts like `skills/scripts/refresh-tool-index.ps1` and `skills/scripts/bootstrap-reverse.ps1` handle tool detection and installation without manual intervention.
- The `skills/scripts/master-route.ps1` script initiates workflows by parsing keyword hints and navigating the routing matrix.
- Downstream skills such as `pwn-chain` automatically receive completed PoCs for further exploit development.

## Frequently Asked Questions

### What prerequisites are required for running the patch-diff-exploit skill?

Analysts need PowerShell or Bash execution capabilities, Git for repository cloning, and sufficient disk space for storing before-and-after binary patches. The bootstrap scripts automatically handle installation of specialized tools like BinDiff, Ghidra, or ghidriff when they are not detected in the system PATH.

### Does the patch-diff-exploit workflow support both Windows and Linux targets?

Yes. The skill accommodates Windows patches (MSU/MSP files) and Linux packages (DEB/RPM formats). The routing system automatically adjusts tool recommendations based on the target platform identified in the analysis hint.

### How does the routing system determine which skill to execute?

The `skills/scripts/master-route.ps1` script parses the `-Hint` parameter and consults [`skills/config/routing.json`](https://github.com/zhaoxuya520/reverse-skill/blob/main/skills/config/routing.json) to match keywords such as "N-day", "patch diff", or "exploit" against registered skill paths. This matrix-based approach ensures accurate workflow selection without manual directory navigation.

### What is the difference between the patch-diff-exploit skill and 0-day research workflows?

The `patch-diff-exploit` skill specifically targets N-day vulnerabilities where vendor patches already exist, using binary diffing to identify the patched bug class. Zero-day research would typically begin with the `fuzzing` or `vuln-research` skills in the same repository, which focus on discovering previously unknown vulnerabilities rather than analyzing existing patches.