CVE-2021-21425 — AI Deep Analysis Summary

Q: What is this vulnerability? (Essence + Consequences)

🚨 **Essence**: Grav CMS allows unauthenticated users to execute admin controller methods. 💥 **Consequences**: Arbitrary YAML write/update leads to **Remote Code Execution (RCE)**. Critical integrity loss!

Q: Root Cause? (CWE/Flaw)

🛡️ **Root Cause**: CWE-284 (Improper Access Control). The flaw lies in missing authentication checks for specific admin API endpoints. 📉 **Flaw**: No credentials required for sensitive actions.

Q: Who is affected? (Versions/Components)

📦 **Affected**: Grav CMS (Personal blogs, small content platforms). 🏷️ **Vendor**: getgrav. 🧩 **Component**: grav-plugin-admin. ⚠️ **Version**: Specifically noted 1.7.10 and 1.10.7 in PoCs.

Q: What can hackers do? (Privileges/Data)

👑 **Privileges**: Full Admin access without login! 📝 **Data**: Can write/update arbitrary YAML files. 💻 **Impact**: Execute arbitrary code on the server. Total system compromise.

Q: Is exploitation threshold high? (Auth/Config)

📉 **Threshold**: LOW. 🔓 **Auth**: None required (Unauthenticated). 🌐 **Network**: Remote (AV:N). 🖱️ **UI**: None required. Easy to exploit!

Q: Is there a public Exp? (PoC/Wild Exploitation)

🔥 **Public Exp?**: YES. Multiple PoCs available on GitHub (e.g., CsEnox, bluetoothStrawberry). 📜 **Nmap Scripts**: Public NSE scripts exist for detection. Wild exploitation is possible.

Q: How to self-check? (Features/Scanning)

🔍 **Self-Check**: Use Nmap with `grav_cms.nse` script. 🌐 **Manual**: Try accessing admin API endpoints directly. 📊 **CVSS**: High severity (I:H). Check for unpatched Grav installations.

Q: Is it fixed officially? (Patch/Mitigation)

🛡️ **Official Fix**: Yes. GHSA-6f53-6qgv-39pj advisory exists. 🔄 **Action**: Update `grav-plugin-admin` to the latest patched version immediately. Check vendor site.

Q: What if no patch? (Workaround)

🚧 **No Patch?**: Block access to admin API endpoints via WAF/ACL. 🔒 **Restrict**: Disable YAML write capabilities if possible. 🛑 **Isolate**: Limit network access to the CMS server.

Q: Is it urgent? (Priority Suggestion)

🚨 **Urgency**: CRITICAL. 📅 **Published**: April 2021. ⚡ **Risk**: RCE without auth. 🏃 **Action**: Patch NOW. Do not ignore. High impact on confidentiality and integrity.

Updated May 08, 2026 CVSS 9.3 · Critical

This is a summary of the AI-generated 10-question deep analysis. The full version (longer answers, follow-up Q&A, related CVEs) requires login. Read the full analysis →

Q1What is this vulnerability? (Essence + Consequences)

🚨 **Essence**: Grav CMS allows unauthenticated users to execute admin controller methods. 💥 **Consequences**: Arbitrary YAML write/update leads to **Remote Code Execution (RCE)**. Critical integrity loss!

Q2Root Cause? (CWE/Flaw)

🛡️ **Root Cause**: CWE-284 (Improper Access Control). The flaw lies in missing authentication checks for specific admin API endpoints. 📉 **Flaw**: No credentials required for sensitive actions.

Q3Who is affected? (Versions/Components)

📦 **Affected**: Grav CMS (Personal blogs, small content platforms). 🏷️ **Vendor**: getgrav. 🧩 **Component**: grav-plugin-admin. ⚠️ **Version**: Specifically noted 1.7.10 and 1.10.7 in PoCs.

Q4What can hackers do? (Privileges/Data)

👑 **Privileges**: Full Admin access without login! 📝 **Data**: Can write/update arbitrary YAML files. 💻 **Impact**: Execute arbitrary code on the server. Total system compromise.

Q5Is exploitation threshold high? (Auth/Config)

📉 **Threshold**: LOW. 🔓 **Auth**: None required (Unauthenticated). 🌐 **Network**: Remote (AV:N). 🖱️ **UI**: None required. Easy to exploit!

Q6Is there a public Exp? (PoC/Wild Exploitation)

🔥 **Public Exp?**: YES. Multiple PoCs available on GitHub (e.g., CsEnox, bluetoothStrawberry). 📜 **Nmap Scripts**: Public NSE scripts exist for detection. Wild exploitation is possible.

Q7How to self-check? (Features/Scanning)

🔍 **Self-Check**: Use Nmap with `grav_cms.nse` script. 🌐 **Manual**: Try accessing admin API endpoints directly. 📊 **CVSS**: High severity (I:H). Check for unpatched Grav installations.

Q8Is it fixed officially? (Patch/Mitigation)

🛡️ **Official Fix**: Yes. GHSA-6f53-6qgv-39pj advisory exists. 🔄 **Action**: Update `grav-plugin-admin` to the latest patched version immediately. Check vendor site.

Q9What if no patch? (Workaround)

🚧 **No Patch?**: Block access to admin API endpoints via WAF/ACL. 🔒 **Restrict**: Disable YAML write capabilities if possible. 🛑 **Isolate**: Limit network access to the CMS server.

Q10Is it urgent? (Priority Suggestion)

🚨 **Urgency**: CRITICAL. 📅 **Published**: April 2021. ⚡ **Risk**: RCE without auth. 🏃 **Action**: Patch NOW. Do not ignore. High impact on confidentiality and integrity.

Continue exploring

Vulnerability detail Full AI analysis (login) getgrav CWE-284