CVE-2025-32433 PoC — Erlang/OTP SSH Vulnerable to Pre-Authentication RCE

Source

https://github.com/bilalz5-github/Erlang-OTP-SSH-CVE-2025-32433

Associated Vulnerability

Title: Erlang/OTP SSH Vulnerable to Pre-Authentication RCE (CVE-2025-32433)
Description:Erlang/OTP is a set of libraries for the Erlang programming language. Prior to versions OTP-27.3.3, OTP-26.2.5.11, and OTP-25.3.2.20, a SSH server may allow an attacker to perform unauthenticated remote code execution (RCE). By exploiting a flaw in SSH protocol message handling, a malicious actor could gain unauthorized access to affected systems and execute arbitrary commands without valid credentials. This issue is patched in versions OTP-27.3.3, OTP-26.2.5.11, and OTP-25.3.2.20. A temporary workaround involves disabling the SSH server or to prevent access via firewall rules.

Description

CVE-2025-32433 – Erlang/OTP SSH vulnerability allowing pre-auth RCE

Readme

## ✅ Result

The server responded to an **SSH message ID 80 (0x50)** — which is reserved for post-auth. This proves the server accepts invalid messages during the pre-auth phase, indicating **vulnerable behavior as defined in CVE-2025-32433**.

<img width="959" alt="Python code is executed" src="https://github.com/user-attachments/assets/b5253b1a-ca28-486f-9433-580a157739a1" />

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## 📖 Research Summary

I built this lab after studying Erlang/OTP and the CVE from various trusted sources.

**Erlang/OTP** is a powerful environment originally developed by Ericsson to build scalable and fault-tolerant distributed systems. It includes its own **SSH server implementation**. The SSH module inside Erlang/OTP is vulnerable to **unauthenticated remote code execution (RCE)** due to incorrect handling of **SSH message types ≥ 80 during the pre-auth phase**.

Instead of rejecting these invalid messages, the server processes them — which allows an attacker to craft malicious messages and potentially gain unauthorized code execution access.

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### 🔍 Key Things I Learned

- **Erlang/OTP SSH** allows secure shell/file access within Erlang systems  
- **Message ID 80+** is reserved for post-authentication but can be abused pre-auth  
- **Detection**: Suricata or NIDS can spot “SSH_MSG_CHANNEL_REQUEST” with “exec” commands  
- **Affected Versions**:
  - OTP-27.3.2 and below
  - OTP-26.2.5.10 and below
  - OTP-25.3.2.19 and below  
- **Patched Versions**:
  - OTP-27.3.3
  - OTP-26.2.5.11
  - OTP-25.3.2.20

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### 📚 Credits & Reference

- [GitHub Security Advisory – GHSA-37cp-fgq5-7wc2](https://github.com/erlang/otp/security/advisories/GHSA-37cp-fgq5-7wc2)  
- Research PoC and writeups by [Matthew Keeley](https://github.com/ProDefense/CVE-2025-32433)  
- Community detection insights via Suricata, Wireshark, and FortiGate  
- Official Erlang/OTP documentation and CVE pages

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### 💬 Final Note  
*Not all content here is 100% original — I built the lab & PoC myself but studied from multiple sources to understand Erlang, OTP, SSH, and CVE-2025-32433 clearly. This README reflects my own summary and learning.* 🤝

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