CVE-2021-3493 — AI Deep Analysis Summary

Q: Who is affected? (Versions/Components)

📦 **Affected**: Ubuntu Linux Kernel. 📅 **Versions**: 14.04 ESM, 16.04 LTS, 18.04 LTS, 19.04, 20.04 LTS, 20.10. ⚠️ Specifically targets Ubuntu's specific kernel patches.

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

💀 **Action**: Local Privilege Escalation. 🔓 **Result**: Gain **Root** privileges. 📂 **Access**: Full control over files, data, and system configurations. No data loss, but total compromise.

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

⚖️ **Threshold**: Low. 📝 **Auth**: Requires **Local** access (low privilege). 🖱️ **UI**: No user interaction needed. 🌐 **Network**: Not remote exploitable. Must be on the machine.

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

💣 **Exploit**: YES. Public PoCs available on GitHub (e.g., briskets, oneoy). 🛠️ **Usage**: Simple `gcc` compilation and execution. 🌍 **Wild**: Active exploitation is highly likely given ease of use.

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

🔍 **Check**: Scan for Ubuntu versions listed above. 📜 **Kernel**: Check kernel version < 5.11. 🧪 **Test**: Run known PoC scripts in isolated env. 📊 **Tools**: Use vulnerability scanners detecting CVE-2021-3493.

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

✅ **Fixed**: YES. 📅 **Patch**: Fixed in Linux Kernel **5.11**. 🔄 **Action**: Update Ubuntu OS and Kernel immediately. Ubuntu Security Notices (USN-4917-1) provide patches.

Q: What if no patch? (Workaround)

🚧 **Workaround**: If patching is delayed, restrict unprivileged user namespaces. 🛑 **Limit**: Disable unprivileged overlayfs mounts via sysctl or kernel parameters. 📉 **Risk**: Mitigates but doesn't eliminate risk.

Q: Is it urgent? (Priority Suggestion)

🔥 **Priority**: CRITICAL. 🚀 **Urgency**: HIGH. 📉 **CVSS**: 8.8 (High). ⚡ **Action**: Patch immediately. Local attackers can easily escalate to root. Do not ignore.

Updated May 06, 2026 CVSS 8.8 · High

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**: A critical Linux Kernel flaw in Ubuntu's OverlayFS. 📉 **Consequences**: Allows local privilege escalation.…

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Q2Root Cause? (CWE/Flaw)

🛡️ **CWE-270**: Privilege Context Incorrectness. 🐛 **Flaw**: Ubuntu's patch allowing unprivileged overlayfs mounts failed to properly validate file system capabilities against user namespaces.…

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Q3Who is affected? (Versions/Components)

📦 **Affected**: Ubuntu Linux Kernel. 📅 **Versions**: 14.04 ESM, 16.04 LTS, 18.04 LTS, 19.04, 20.04 LTS, 20.10. ⚠️ Specifically targets Ubuntu's specific kernel patches.

Q4What can hackers do? (Privileges/Data)

💀 **Action**: Local Privilege Escalation. 🔓 **Result**: Gain **Root** privileges. 📂 **Access**: Full control over files, data, and system configurations. No data loss, but total compromise.

Q5Is exploitation threshold high? (Auth/Config)

⚖️ **Threshold**: Low. 📝 **Auth**: Requires **Local** access (low privilege). 🖱️ **UI**: No user interaction needed. 🌐 **Network**: Not remote exploitable. Must be on the machine.

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

💣 **Exploit**: YES. Public PoCs available on GitHub (e.g., briskets, oneoy). 🛠️ **Usage**: Simple `gcc` compilation and execution. 🌍 **Wild**: Active exploitation is highly likely given ease of use.

Q7How to self-check? (Features/Scanning)

🔍 **Check**: Scan for Ubuntu versions listed above. 📜 **Kernel**: Check kernel version < 5.11. 🧪 **Test**: Run known PoC scripts in isolated env. 📊 **Tools**: Use vulnerability scanners detecting CVE-2021-3493.

Q8Is it fixed officially? (Patch/Mitigation)

✅ **Fixed**: YES. 📅 **Patch**: Fixed in Linux Kernel **5.11**. 🔄 **Action**: Update Ubuntu OS and Kernel immediately. Ubuntu Security Notices (USN-4917-1) provide patches.

Q9What if no patch? (Workaround)

🚧 **Workaround**: If patching is delayed, restrict unprivileged user namespaces. 🛑 **Limit**: Disable unprivileged overlayfs mounts via sysctl or kernel parameters. 📉 **Risk**: Mitigates but doesn't eliminate risk.

Q10Is it urgent? (Priority Suggestion)

🔥 **Priority**: CRITICAL. 🚀 **Urgency**: HIGH. 📉 **CVSS**: 8.8 (High). ⚡ **Action**: Patch immediately. Local attackers can easily escalate to root. Do not ignore.

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Vulnerability detail Full AI analysis (login) Ubuntu CWE-270