CVE-2026-42376 — AI Deep Analysis Summary

🚨 **Essence**: A hardcoded Telnet backdoor in D-Link DIR-456U A1. 📉 **Consequences**: Attackers gain full **root shell** access. Complete loss of confidentiality, integrity, and availability.…

🛡️ **CWE**: CWE-798 (Use of Hard-coded Credentials). 🔍 **Flaw**: The `/etc/init0.d/S80telnetd.sh` script launches a custom `telnetd` with static credentials.…

📦 **Vendor**: D-Link. 📱 **Product**: DIR-456U Firmware. 🚫 **Version**: Hardware Version **A1** only. ⚠️ **Status**: **End-of-Life (EOL)**. No longer supported by the manufacturer.

🔓 **Privileges**: **Root** shell access. 🌐 **Scope**: Local network attackers. 💾 **Data**: Full management control.…

📉 **Threshold**: **LOW**. 🚫 **Auth**: None required (unauthenticated). 🌍 **Network**: Local network access is sufficient. 🎯 **Complexity**: Low (AC:L). No user interaction needed.

📜 **Public Exp**: No specific PoC code listed in references. 📢 **Advisory**: Securin Advisory details the mechanism. 🧠 **Exploitation**: Trivial.…

🔍 **Check**: Scan for Telnet service (Port 23). 🧪 **Test**: Attempt login with user: `Alphanetworks`, pass: `whdrv01_dlob_dir456U`.…

🚫 **Official Patch**: **NO**. 📅 **Status**: Device is **EOL** (End-of-Life). 🛑 **Reality**: D-Link will not release security updates. The vulnerability remains open forever for this hardware revision.

🛡️ **Mitigation**: **Isolate** the device. 🚫 **Block**: Firewall rules to block external access to Port 23. 🧹 **Disable**: If possible, disable Telnet service via configuration (if accessible).…

🔥 **Urgency**: **CRITICAL**. 📈 **Risk**: CVSS 10.0 (High). ⚠️ **Reason**: Unauthenticated, full root access, EOL status means no fix. Immediate isolation or replacement is mandatory to prevent compromise.