CVE-2023-52976 – A NULL pointer dereference vulnerability in the... (How to Fix)

Q: What is the severity of CVE-2023-52976?

CVE-2023-52976 has a CVSS score of 5.5 (MEDIUM). A NULL pointer dereference vulnerability in the Linux kernel's EFI subsystem could cause kernel panic or system crash when the efi_mem_reserve_persistent function fails to properly handle memory mapping failures. This affects Linux systems using EFI firmware with persistent memory reservations. The vulnerability requires local access to trigger.

📋 TL;DR

A NULL pointer dereference vulnerability in the Linux kernel's EFI subsystem could cause kernel panic or system crash when the efi_mem_reserve_persistent function fails to properly handle memory mapping failures. This affects Linux systems using EFI firmware with persistent memory reservations. The vulnerability requires local access to trigger.

💻 Affected Systems

Products:

Linux Kernel

Versions: Specific affected versions not explicitly stated in CVE, but patches available for multiple stable branches

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems using EFI firmware with persistent memory reservations enabled. Most modern Linux systems with UEFI firmware are potentially 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...

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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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to system crash and denial of service, potentially causing data loss or service disruption.

🟠

Likely Case

System crash or kernel panic when specific EFI memory operations fail, requiring reboot to restore service.

🟢

If Mitigated

Minor service interruption with automatic recovery after reboot if systems are properly monitored.

🌐 Internet-Facing: LOW - Requires local access to trigger, not remotely exploitable.

🏢 Internal Only: MEDIUM - Local attackers or malicious processes could crash systems, but requires specific conditions to trigger.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and ability to trigger specific EFI memory operations. Not trivial to exploit reliably.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Multiple stable kernel versions with fixes (see git commit references in CVE)

Vendor Advisory: https://git.kernel.org/stable/c/87d4ff18738fd71e7e3c10827c80257da6283697

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from your distribution's repositories. 2. For custom kernels, apply the fix from git.kernel.org. 3. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable EFI persistent memory reservations

linux

Prevent use of the vulnerable code path by disabling EFI persistent memory features

echo 0 > /sys/firmware/efi/efivars/persistent_memory_reservations (if available)
Add 'noefi' to kernel boot parameters

🧯 If You Can't Patch

Restrict local access to systems to prevent malicious users from triggering the vulnerability
Implement monitoring for kernel panics and system crashes with rapid response procedures

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with patched versions from git.kernel.org references. Systems with unpatched kernels using EFI are vulnerable.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version after update matches patched versions. Check that system doesn't crash when performing EFI memory operations.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages in /var/log/kern.log or dmesg
System crash/reboot events
NULL pointer dereference errors in kernel logs

Network Indicators:

Sudden loss of connectivity from affected systems

SIEM Query:

source="kernel" AND ("NULL pointer dereference" OR "kernel panic" OR "efi_mem_reserve_persistent")

📊 Metadata

CVE ID: CVE-2023-52976

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

EPSS Score: 0.04% exploit probability (13.3th percentile)

Published: March 27, 2025

Last Updated: October 1, 2025

🔗 References

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