CVE-2021-47279 – This CVE describes a null pointer dereference v... (How to Fix)

Q: What is the severity of CVE-2021-47279?

CVE-2021-47279 has a CVSS score of 5.5 (MEDIUM). This CVE describes a null pointer dereference vulnerability in the Linux kernel's Broadcom STB USB pinmap driver. If exploited, it could cause a kernel panic or system crash. Systems using affected Linux kernel versions with the brcmstb-usb-pinmap driver loaded are vulnerable.

📋 TL;DR

This CVE describes a null pointer dereference vulnerability in the Linux kernel's Broadcom STB USB pinmap driver. If exploited, it could cause a kernel panic or system crash. Systems using affected Linux kernel versions with the brcmstb-usb-pinmap driver loaded are vulnerable.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected kernel versions not specified in CVE description, but patches exist in stable branches.

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable if the brcmstb-usb-pinmap driver is loaded (typically on Broadcom STB hardware). Most general-purpose Linux systems are not affected.

📦 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

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

🟠

Likely Case

System crash or kernel panic resulting in temporary denial of service until system reboot.

🟢

If Mitigated

No impact if driver is not loaded or system is patched.

🌐 Internet-Facing: LOW - This requires local access or ability to load kernel modules.

🏢 Internal Only: MEDIUM - Local users or processes could potentially trigger the vulnerability to cause denial of service.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and ability to trigger the specific driver code path. No known public exploits.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patched in Linux kernel stable releases. Check specific distribution kernel versions.

Vendor Advisory: https://git.kernel.org/stable/c/2147684be1ebdaf845783139b9bc4eba3fecd9e4

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from your distribution. 2. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable brcmstb-usb-pinmap driver

linux

Prevent loading of vulnerable driver module

echo 'blacklist brcmstb-usb-pinmap' >> /etc/modprobe.d/blacklist.conf
rmmod brcmstb-usb-pinmap

🧯 If You Can't Patch

Ensure brcmstb-usb-pinmap driver is not loaded on systems without Broadcom STB hardware
Restrict local user access to systems where driver must remain loaded

🔍 How to Verify

Check if Vulnerable:

Check if brcmstb-usb-pinmap driver is loaded: lsmod | grep brcmstb-usb-pinmap

Check Version:

uname -r

Verify Fix Applied:

Check kernel version against distribution security advisories and verify driver version

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages in /var/log/kern.log or dmesg
System crash/reboot events

Network Indicators:

None - local vulnerability only

SIEM Query:

Search for kernel panic events or unexpected system reboots on Linux hosts

📊 Metadata

CVE ID: CVE-2021-47279

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-476

Published: May 21, 2024

Last Updated: December 26, 2024

🔗 References

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🔗 Related Vulnerabilities

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