CVE-2021-45420 — AI Deep Analysis Summary

🚨 **Essence**: Arbitrary File Write via unauthenticated CGI scripts. 📉 **Consequences**: Denial of Service (DoS) or Remote Code Execution (RCE). Attackers can overwrite system files without permission.

🛡️ **Root Cause**: Lack of Authentication Mechanism. 🐛 **Flaw**: Unrestricted access to `/cgi-bin/logo_extra_upload.cgi`, `/cgi-bin/cal_save.cgi`, and `/cgi-bin/lo_utils.cgi` allows writing any file.

🏭 **Affected**: Emerson Xweb-500 (Dixell XWEB-500). 📅 **Status**: Product support ended in 2018. ⚠️ **Note**: Should be removed or replaced immediately.

💻 **Privileges**: No authentication required. 📂 **Data/Action**: Write ANY file to the target system. 🎯 **Impact**: Can crash the system (DoS) or potentially execute remote code (RCE).

🔓 **Threshold**: VERY LOW. 🚫 **Auth**: None needed. 🌐 **Config**: Direct access to CGI endpoints is sufficient. Easy to exploit for anyone with network access.

🔍 **Public Exp**: YES. 📜 **PoC**: Available via ProjectDiscovery Nuclei templates. 📂 **Files**: Specific YAML templates target the vulnerable CGI paths directly.

🔎 **Self-Check**: Scan for the specific CGI paths: `/cgi-bin/logo_extra_upload.cgi`, `/cgi-bin/cal_save.cgi`, `/cgi-bin/lo_utils.cgi`.…

🚫 **Official Fix**: NO. 📅 **Timeline**: Support ended in 2018. 📢 **Advice**: Vendor recommends removal or replacement, not patching.

🛡️ **Workaround**: Isolate the device from the network. 🗑️ **Action**: Decommission the Xweb-500 immediately. 🚫 **Block**: Restrict access to CGI-bin directories via firewall rules if replacement isn't immediate.

🔥 **Urgency**: CRITICAL. 🚨 **Priority**: HIGH. ⚡ **Reason**: No auth needed + No patch available + High impact (RCE/DoS). Treat as active threat.