CVE-2024-42070: Linux Kernel Information Disclosure Flaw

CVE-2024-42070 Overview

CVE-2024-42070 is a memory leak vulnerability in the Linux kernel's netfilter subsystem, specifically within the nf_tables component. The vulnerability exists due to incomplete validation of NFT_DATA_VALUE during store operations to data registers. When register store validation for NFT_DATA_VALUE is conditional, but the datatype is always either NFT_DATA_VALUE or NFT_DATA_VERDICT, a pointer to chain object can be leaked through the registers.

This vulnerability requires local access and low privileges to exploit, potentially allowing an attacker to cause a denial of service through memory resource exhaustion on affected Linux systems.

Critical Impact

Local attackers with low privileges can exploit this memory leak vulnerability to potentially cause denial of service conditions by exhausting kernel memory resources through leaked chain object pointers in the nf_tables subsystem.

Affected Products

• Linux Kernel (multiple versions)
• Systems running nf_tables/netfilter subsystem
• Debian-based distributions (referenced in LTS announcements)

Discovery Timeline

• July 29, 2024 - CVE-2024-42070 published to NVD
• November 3, 2025 - Last updated in NVD database

Technical Details for CVE-2024-42070

Vulnerability Analysis

The vulnerability resides in the nf_tables module of the Linux kernel's netfilter framework. The root issue stems from how register store operations handle data type validation. The NFT_DATA_VALUE validation was implemented conditionally, despite the fact that the datatype must always be either NFT_DATA_VALUE or NFT_DATA_VERDICT.

This conditional check creates a gap in validation coverage where pointers to internal chain objects can be improperly stored in registers and subsequently leaked. The fix introduces a new helper function that infers the register type from the set datatype, eliminating the conditional check and ensuring complete validation coverage for all register store operations.

The impact is classified as a denial of service through memory exhaustion (CWE-401: Missing Release of Memory after Effective Lifetime), as the leaked chain object pointers can accumulate and consume kernel memory resources over time.

Root Cause

The root cause is incomplete input validation in the nf_tables register store mechanism. The validation logic for NFT_DATA_VALUE was conditional when it should have been unconditional. Since datatypes in nf_tables are binary (either NFT_DATA_VALUE or NFT_DATA_VERDICT), the conditional check was unnecessary and left a validation gap that could result in chain object pointer leakage.

The fix addresses this by implementing a helper function to properly infer register types from set datatypes, removing the problematic conditional validation and ensuring all register stores are fully validated.

Attack Vector

The attack vector is local, requiring an authenticated user with low privileges to interact with the netfilter/nf_tables subsystem. An attacker would need to:

1. Gain local access to a vulnerable Linux system
2. Interact with the nf_tables subsystem to trigger register store operations
3. Exploit the incomplete validation to leak chain object pointers
4. Repeatedly trigger the vulnerability to exhaust kernel memory resources

The vulnerability requires no user interaction and has no scope change, affecting only the availability of the system.

Detection Methods for CVE-2024-42070

Indicators of Compromise

• Unexpected memory growth in kernel space related to netfilter subsystem
• System instability or out-of-memory conditions without obvious cause
• Unusual nf_tables activity patterns in system logs
• Kernel messages indicating memory allocation failures in netfilter components

Detection Strategies

• Monitor kernel memory usage patterns, particularly in the nf_tables/netfilter subsystem
• Implement kernel auditing for nf_tables register operations
• Use kernel memory leak detection tools (kmemleak) to identify leaked chain objects
• Deploy SentinelOne Singularity Platform for real-time kernel-level threat detection

Monitoring Recommendations

• Enable kernel memory debugging options in development/testing environments
• Configure alerts for abnormal memory consumption trends
• Monitor syslog for netfilter-related warnings or errors
• Implement baseline memory usage monitoring for comparison against anomalous behavior

How to Mitigate CVE-2024-42070

Immediate Actions Required

• Update Linux kernel to a patched version as soon as possible
• Review system exposure and limit local user access where feasible
• Monitor systems for signs of memory exhaustion or unusual netfilter activity
• Consider temporarily restricting access to nf_tables functionality for non-privileged users if patches cannot be immediately applied

Patch Information

The Linux kernel maintainers have released patches across multiple stable kernel branches. The fix introduces a helper function to properly infer register types from set datatypes, removing the conditional validation that caused the vulnerability.

Patches are available through the following kernel git commits:

• Kernel Git Commit 23752737c6a6
• Kernel Git Commit 40188a25a984
• Kernel Git Commit 41a6375d48de
• Kernel Git Commit 461302e07f49
• Kernel Git Commit 5d43d789b579
• Kernel Git Commit 7931d32955e0
• Kernel Git Commit 952bf8df2225
• Kernel Git Commit efb27ad05949

Debian users should refer to the Debian LTS Announcement for distribution-specific update instructions.

Workarounds

• Restrict local user access to minimize potential attack surface
• Limit access to nf_tables/netfilter configuration interfaces for non-administrative users
• Implement memory usage monitoring and alerting to detect exploitation attempts
• Consider using containerization or virtualization to isolate workloads until patches can be applied

# Check current kernel version
uname -r

# Update kernel on Debian-based systems
sudo apt update && sudo apt upgrade linux-image-$(uname -r)

# Verify nf_tables module status
lsmod | grep nf_tables

# Monitor kernel memory usage
cat /proc/meminfo | grep -E "(MemFree|Slab|SReclaimable)"