CVE-2021-47334 – This CVE describes a use-after-free vulnerabili... (How to Fix)

Q: What is the severity of CVE-2021-47334?

CVE-2021-47334 has a CVSS score of 7.8 (HIGH). This CVE describes a use-after-free vulnerability in the Linux kernel's ibmasm driver module. When device initialization fails, the system attempts to free already-freed memory, potentially allowing local attackers to execute arbitrary code or crash the system. This affects Linux systems with the ibmasm module loaded.

📋 TL;DR

This CVE describes a use-after-free vulnerability in the Linux kernel's ibmasm driver module. When device initialization fails, the system attempts to free already-freed memory, potentially allowing local attackers to execute arbitrary code or crash the system. This affects Linux systems with the ibmasm module loaded.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific kernel versions with the vulnerable ibmasm module code

Operating Systems: Linux distributions with vulnerable kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable if the ibmasm module is loaded (typically for IBM Advanced System Management hardware). Most standard Linux installations do not load this module by default.

📦 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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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

Local privilege escalation to kernel-level code execution, potentially leading to full system compromise.

🟠

Likely Case

Kernel panic leading to system crash and denial of service.

🟢

If Mitigated

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

🌐 Internet-Facing: LOW - Requires local access to exploit.

🏢 Internal Only: MEDIUM - Local users or compromised accounts could exploit this vulnerability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and ability to trigger the specific error condition during device initialization.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions with the fix applied (see git commits in references)

Vendor Advisory: https://git.kernel.org/stable/c/1512e7dc5eb08b7d92a12e2bfcd9cb8c4a1ec069

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version. 2. Reboot system. 3. Verify ibmasm module is not loaded unless required.

🔧 Temporary Workarounds

Disable ibmasm module

linux

Prevent loading of the vulnerable ibmasm module

echo 'blacklist ibmasm' >> /etc/modprobe.d/blacklist.conf
rmmod ibmasm

🧯 If You Can't Patch

Ensure ibmasm module is not loaded (check with lsmod)
Restrict local user access to systems where module might be loaded

🔍 How to Verify

Check if Vulnerable:

Check if ibmasm module is loaded: lsmod | grep ibmasm

Check Version:

uname -r

Verify Fix Applied:

Check kernel version is patched and ibmasm module is either not loaded or from patched kernel

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs
System crash dumps
Unexpected ibmasm module errors

Network Indicators:

None - local exploitation only

SIEM Query:

Search for kernel panic events or ibmasm module failure messages in system logs

📊 Metadata

CVE ID: CVE-2021-47334

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

📤 Share & Export

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🔗 Related Vulnerabilities

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