CVE-2021-47453 – This CVE describes a memory management vulnerab... (How to Fix)

Q: What is the severity of CVE-2021-47453?

CVE-2021-47453 has a CVSS score of 5.5 (MEDIUM). This CVE describes a memory management vulnerability in the Linux kernel's ice driver that could cause a kernel crash when unloading the driver. The issue occurs when the driver attempts to free an IDA (ID Allocator) that wasn't properly initialized, potentially leading to system instability. Systems using the affected ice network driver with RDMA support are primarily affected.

📋 TL;DR

This CVE describes a memory management vulnerability in the Linux kernel's ice driver that could cause a kernel crash when unloading the driver. The issue occurs when the driver attempts to free an IDA (ID Allocator) that wasn't properly initialized, potentially leading to system instability. Systems using the affected ice network driver with RDMA support are primarily affected.

💻 Affected Systems

Products:

Linux kernel ice network driver

Versions: Linux kernel versions with the vulnerable ice driver code prior to the fix commits

Operating Systems: Linux distributions using the affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires the ice driver to be loaded and RDMA support to be in a specific state where the driver was probed with RDMA support but later entered a state without RDMA support.

📦 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...

Learn more about Linux Kernel →

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...

Learn more about Linux Kernel →

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...

Learn more about Linux Kernel →

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...

Learn more about Linux Kernel →

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...

Learn more about Linux Kernel →

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...

Learn more about Linux Kernel →

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...

Learn more about Linux Kernel →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to system crash and denial of service, potentially requiring physical access to reboot the system.

🟠

Likely Case

System instability or crash when unloading the ice driver module, causing temporary service disruption.

🟢

If Mitigated

No impact if the driver isn't loaded or if the patch is applied.

🌐 Internet-Facing: LOW - This requires local access to unload kernel modules, which typically requires root privileges.

🏢 Internal Only: MEDIUM - Authorized administrators or users with root access could trigger this vulnerability, potentially causing service disruption.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires root privileges to unload kernel modules and specific conditions where RDMA support state changes after driver initialization.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits 73e30a62b19b9fbb4e6a3465c59da186630d5f2e and 777682e59840e24e6c5672197e6ffbcf4bff823b

Vendor Advisory: https://git.kernel.org/stable/c/73e30a62b19b9fbb4e6a3465c59da186630d5f2e

Restart Required: Yes

Instructions:

1. Update to a patched Linux kernel version containing the fix commits. 2. Reboot the system to load the new kernel. 3. Verify the ice driver loads without issues.

🔧 Temporary Workarounds

Prevent ice driver unloading

linux

Prevent unloading of the ice kernel module to avoid triggering the vulnerability

echo 'install ice /bin/false' >> /etc/modprobe.d/ice-blacklist.conf

Disable RDMA support

linux

Disable RDMA functionality in the ice driver if not required

modprobe -r ice
modprobe ice rdma=0

🧯 If You Can't Patch

Restrict root access to prevent unauthorized users from unloading kernel modules
Monitor system logs for ice driver unload attempts and investigate any suspicious activity

🔍 How to Verify

Check if Vulnerable:

Check if the ice driver is loaded and examine kernel version against patched versions: lsmod | grep ice && uname -r

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes the fix commits and test unloading/reloading the ice driver: modprobe -r ice && modprobe ice

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages in /var/log/messages or dmesg
Ice driver unload failures or crashes in system logs

Network Indicators:

Sudden loss of network connectivity on interfaces using ice driver

SIEM Query:

source="kernel" AND ("panic" OR "Oops" OR "ice" AND ("unload" OR "free" OR "crash"))

📊 Metadata

CVE ID: CVE-2021-47453

CVSS v3 Score: 5.5 (MEDIUM)

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

CWE: CWE-401

Published: May 22, 2024

Last Updated: September 24, 2025

🔗 References

📤 Share & Export

📄 Export Markdown 📋 Export JSON

🔗 Related Vulnerabilities

If you're affected by CVE-2021-47453, you might also want to check these: