CVE-2022-41222: Linux Kernel Use-After-Free Vulnerability

CVE-2022-41222 Overview

CVE-2022-41222 is a use-after-free vulnerability discovered in the Linux kernel's memory management subsystem, specifically in mm/mremap.c. The vulnerability exists in kernel versions before 5.13.3 and stems from improper handling of rmap (reverse mapping) locks during PUD (Page Upper Directory) move operations. This flaw can lead to a stale TLB (Translation Lookaside Buffer) condition, enabling potential privilege escalation or system compromise by a local attacker with low-level privileges.

Critical Impact

Local attackers with low privileges can exploit this use-after-free vulnerability to potentially achieve privilege escalation, arbitrary code execution, or cause denial of service conditions on affected Linux systems.

Affected Products

• Linux Kernel (versions before 5.13.3)
• Debian Linux 10.0
• Canonical Ubuntu Linux 18.04 LTS, 20.04 LTS, 22.04 LTS
• NetApp HCI Baseboard Management Controller (H300S, H410C, H410S, H500S, H700S)

Discovery Timeline

• 2022-09-21 - CVE-2022-41222 published to NVD
• 2025-05-28 - Last updated in NVD database

Technical Details for CVE-2022-41222

Vulnerability Analysis

This vulnerability is classified as CWE-416 (Use After Free) and affects the mremap system call implementation in the Linux kernel. The flaw occurs when the kernel fails to properly hold an rmap lock during a PUD move operation, creating a race condition that can result in use-after-free memory access through a stale TLB entry.

The attack requires local access to the system and involves high complexity due to the race condition nature of the vulnerability. An attacker must successfully win a race to exploit the stale TLB condition. Despite the complexity, successful exploitation can lead to high impacts on confidentiality, integrity, and availability—potentially allowing an attacker to read sensitive kernel memory, modify kernel data structures, or crash the system.

Root Cause

The root cause lies in the improper synchronization within mm/mremap.c. When performing a PUD move operation, the kernel fails to acquire and hold the necessary rmap lock. This missing lock creates a window where the TLB can contain stale entries pointing to memory that has already been freed or reallocated. The race condition between the TLB flush and the memory deallocation enables the use-after-free scenario.

Attack Vector

The vulnerability requires local access to the target system. An attacker with low-privilege access must craft a specific sequence of memory operations involving the mremap() system call to trigger the race condition. The attack involves:

1. Mapping memory regions that will trigger PUD-level page table operations
2. Initiating concurrent mremap() operations to create the race condition
3. Timing the operations to exploit the window where the rmap lock is not held
4. Accessing memory through the stale TLB entry before it is invalidated

Due to the race condition nature, the attack may require multiple attempts to succeed, but the high impact on confidentiality, integrity, and availability makes this a significant threat to affected systems.

Detection Methods for CVE-2022-41222

Indicators of Compromise

• Unusual kernel panics or crashes related to memory management subsystems
• Unexpected privilege escalations from low-privilege user accounts
• Anomalous mremap() system call patterns or high frequency of mremap operations
• Kernel log messages indicating memory corruption or invalid page table entries

Detection Strategies

• Monitor system calls using auditd to track suspicious mremap() activity patterns
• Deploy kernel-level endpoint detection to identify use-after-free exploitation attempts
• Implement SentinelOne's behavioral AI to detect anomalous memory operation sequences
• Review kernel logs for TLB-related errors or memory management warnings

Monitoring Recommendations

• Enable kernel auditing for memory management system calls (mremap, mmap, munmap)
• Configure alerting on kernel crash events with stack traces involving mm/mremap.c
• Use SentinelOne's Singularity Platform for real-time kernel-level threat detection
• Monitor for unauthorized privilege changes following mremap system call activity

How to Mitigate CVE-2022-41222

Immediate Actions Required

• Update Linux kernel to version 5.13.3 or later immediately
• Apply vendor-specific security patches for Debian, Ubuntu, and NetApp products
• Restrict local access to only trusted users until patching is complete
• Enable additional kernel hardening options where available

Patch Information

The vulnerability has been addressed in Linux kernel version 5.13.3 and later. The fix ensures proper rmap lock acquisition during PUD move operations. The specific commit addressing this issue is available in the Linux Kernel Commit 97113eb. Detailed changelog information can be found in the Linux Kernel ChangeLog 5.13.3.

For enterprise distributions, refer to:

• Debian LTS Announcement November 2022
• NetApp Security Advisory NTAP-20230214-0008
• Packet Storm Live Patch Notice for live patching options

Workarounds

• Limit local user access to reduce the attack surface until patches can be applied
• Consider implementing kernel live patching solutions for production systems that cannot be immediately rebooted
• Use containerization with restricted syscall profiles (seccomp) to limit mremap() access
• Enable kernel Address Space Layout Randomization (KASLR) to increase exploitation difficulty

# Check current kernel version
uname -r

# For Debian/Ubuntu systems, update the kernel
sudo apt update && sudo apt upgrade linux-image-generic

# Verify the updated kernel version (should be 5.13.3 or later, or patched backport)
dpkg -l | grep linux-image