CVE-2021-47318 – A use-after-free vulnerability in the Linux ker... (How to Fix)

Q: What is the severity of CVE-2021-47318?

CVE-2021-47318 has a CVSS score of 7.8 (HIGH). A use-after-free vulnerability in the Linux kernel's arch_topology subsystem allows race conditions when clearing scale_freq_data structures. This could lead to kernel crashes or potential privilege escalation. Affects Linux systems with specific kernel versions that haven't been patched.

📋 TL;DR

A use-after-free vulnerability in the Linux kernel's arch_topology subsystem allows race conditions when clearing scale_freq_data structures. This could lead to kernel crashes or potential privilege escalation. Affects Linux systems with specific kernel versions that haven't been patched.

💻 Affected Systems

Products:

Linux Kernel

Versions: Specific kernel versions between initial introduction of affected code and patched versions (exact range depends on distribution backports)

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Vulnerability is in core kernel code, so all configurations using affected kernels are vulnerable unless patched.

📦 What is this software?

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

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⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to system crash or potential privilege escalation to kernel mode, allowing complete system compromise.

🟠

Likely Case

System instability, kernel crashes, or denial of service due to memory corruption.

🟢

If Mitigated

Minimal impact with proper kernel hardening and isolation controls in place.

🌐 Internet-Facing: LOW - Requires local access or ability to execute code on the system.

🏢 Internal Only: MEDIUM - Local attackers or malicious users could potentially exploit this vulnerability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires local access and precise timing to trigger the race condition. No public exploits known at this time.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions with commits 83150f5d05f065fb5c12c612f119015cabdcc124 or ccdf7e073170886bc370c613e269de610a794c4a

Vendor Advisory: https://git.kernel.org/stable/c/83150f5d05f065fb5c12c612f119015cabdcc124

Restart Required: Yes

Instructions:

1. Check your kernel version. 2. Update to a patched kernel version from your distribution's repositories. 3. Reboot the system to load the new kernel.

🔧 Temporary Workarounds

No known workarounds

linux

This is a kernel-level vulnerability that requires patching.

🧯 If You Can't Patch

Implement strict access controls to limit local user privileges
Monitor systems for kernel crashes or instability indicators

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with patched versions from your distribution. Vulnerable if using unpatched kernel with affected code.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version after update contains the fix commits: 83150f5d05f065fb5c12c612f119015cabdcc124 or ccdf7e073170886bc370c613e269de610a794c4a

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages in /var/log/messages or dmesg
System crash reports
Unexpected reboots

Network Indicators:

None - local vulnerability only

SIEM Query:

Search for kernel panic or oops messages in system logs

📊 Metadata

CVE ID: CVE-2021-47318

CVSS v3 Score: 7.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-416

Published: May 21, 2024

Last Updated: December 26, 2024

🔗 References

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