CVE-2021-47499 – This CVE describes a memory leak vulnerability ... (How to Fix)

Q: What is the severity of CVE-2021-47499?

CVE-2021-47499 has a CVSS score of 5.5 (MEDIUM). This CVE describes a memory leak vulnerability in the Linux kernel's KXCJK-1013 accelerometer driver. When the ACPI type is ACPI_SMO8500, memory allocated for triggered buffers isn't properly freed, causing gradual memory exhaustion. This affects Linux systems using the kxcjk_1013 driver with specific ACPI configurations.

📋 TL;DR

This CVE describes a memory leak vulnerability in the Linux kernel's KXCJK-1013 accelerometer driver. When the ACPI type is ACPI_SMO8500, memory allocated for triggered buffers isn't properly freed, causing gradual memory exhaustion. This affects Linux systems using the kxcjk_1013 driver with specific ACPI configurations.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific kernel versions containing the vulnerable kxcjk_1013 driver code prior to fixes

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable when kxcjk_1013 driver is loaded and ACPI type is ACPI_SMO8500; requires specific hardware configuration.

📦 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 →

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

Sustained exploitation could lead to kernel memory exhaustion, causing system instability, crashes, or denial of service through resource depletion.

🟠

Likely Case

Gradual memory leak over time leading to degraded system performance and potential kernel panics or OOM killer activation.

🟢

If Mitigated

Minimal impact with proper monitoring and memory limits in place; system remains functional but may experience performance degradation.

🌐 Internet-Facing: LOW - Requires local access or specific hardware configuration; not directly exploitable over network.

🏢 Internal Only: MEDIUM - Affects systems with specific ACPI configurations; could impact embedded devices or servers with vulnerable kernel versions.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: HIGH

Exploitation requires specific hardware configuration (ACPI_SMO8500) and local access; memory leak occurs during normal driver operation rather than through malicious input.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Multiple stable kernel commits listed in references

Vendor Advisory: https://git.kernel.org/stable/c/14508fe13b1c578b3d2ba574f1d48b351975860c

Restart Required: Yes

Instructions:

1. Update to a kernel version containing the fix commits. 2. Check your distribution's security advisories for backported patches. 3. Reboot the system after kernel update.

🔧 Temporary Workarounds

Disable kxcjk_1013 driver

linux

Prevent loading of the vulnerable driver module

echo 'blacklist kxcjk_1013' >> /etc/modprobe.d/blacklist.conf
rmmod kxcjk_1013

Disable ACPI_SMO8500 support

linux

Prevent the specific ACPI configuration that triggers the vulnerability

Add 'acpi=off' or specific ACPI blacklisting to kernel boot parameters

🧯 If You Can't Patch

Monitor system memory usage and implement alerting for abnormal memory consumption
Implement kernel memory limits and restart services if memory usage exceeds thresholds

🔍 How to Verify

Check if Vulnerable:

Check if kxcjk_1013 module is loaded and system has ACPI_SMO8500: lsmod | grep kxcjk_1013 && dmesg | grep -i smo8500

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes fix commits or check /sys/module/kxcjk_1013/taint for no memory leak indicators

📡 Detection & Monitoring

Log Indicators:

Kernel OOM messages
Increasing memory usage in /proc/meminfo
dmesg entries about memory allocation failures

Network Indicators:

None - local vulnerability only

SIEM Query:

source="kernel" AND ("Out of memory" OR "oom-killer" OR "slab allocation failure")

📊 Metadata

CVE ID: CVE-2021-47499

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 24, 2024

Last Updated: January 6, 2025

🔗 References

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