CVE-2021-27850 — AI Deep Analysis Summary

🚨 **Essence**: Critical Unauthenticated Remote Code Execution (RCE). 💥 **Consequences**: Attackers download `AppModule.class` to leak the HMAC Secret Key.…

🛡️ **CWE**: CWE-200 (Information Exposure). 🔍 **Flaw**: The framework exposes the HMAC signing key via a specific URL path (`/assets/.../AppModule.class`). This bypasses the previous fix for CVE-2019-0195.…

🏢 **Vendor**: Apache Software Foundation. 📦 **Product**: Apache Tapestry. 📅 **Affected Versions**: 5.4.5, 5.5.0, 5.6.2, and 5.7.0. ✅ **Fixed In**: Upgrade to version 5.7.1 or later.

👑 **Privileges**: Unauthenticated Remote Code Execution. 🔓 **Data Access**: Leaks the HMAC Secret Key used for signing serialized objects.…

📉 **Threshold**: VERY LOW. 🔑 **Auth**: None required (Unauthenticated). ⚙️ **Config**: Exploitable via standard HTTP requests. 🎯 **Ease**: Simple URL manipulation to extract the key, then use PoC tools for RCE.

🔥 **Public Exp?**: YES. 📂 **PoCs Available**: Multiple GitHub repositories (e.g., `kahla-sec`, `dorkerdevil`, `Ovi3`). 🌐 **Wild Exploitation**: High risk. Tools like Nuclei templates exist for automated scanning.…

🔍 **Self-Check**: 1. Scan for Apache Tapestry versions < 5.7.1. 2. Attempt to access `/assets/.../AppModule.class`. 3. Use Nuclei template `CVE-2021-27850.yaml`. 4.…

🛡️ **Official Fix**: YES. 📥 **Patch**: Upgrade Apache Tapestry to version **5.7.1** or later. 📝 **Note**: This CVE is a bypass of the earlier CVE-2019-0195 fix. Ensure the latest version is applied.

🚧 **No Patch Workaround**: 1. **Block Access**: Restrict access to `/assets/` paths containing `AppModule.class` via WAF or Nginx config. 2. **Network Segmentation**: Limit exposure of Tapestry servers. 3.…

🔴 **Priority**: CRITICAL / URGENT. ⏱️ **Timeline**: Published April 2021, but PoCs are mature and public. 🚀 **Action**: Immediate patching to v5.7.1+ is mandatory.…