CVE-2025-21868
📋 TL;DR
A Linux kernel vulnerability where improper memory allocation handling when MAX_SKB_FRAGS is set to large values (like 45) can cause kernel warnings and potential denial-of-service. This affects Linux systems with custom kernel builds using specific MAX_SKB_FRAGS configurations, particularly during network interface initialization.
💻 Affected Systems
- Linux Kernel
📦 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...
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 or system crash during network stack initialization, preventing system boot or causing unexpected reboots.
Likely Case
Kernel warning messages during boot or network initialization, potentially causing network functionality issues or system instability.
If Mitigated
Minor performance impact from using kmalloc() instead of more efficient allocation methods for small head cache scenarios.
🎯 Exploit Status
This is a configuration-specific issue that triggers during kernel initialization, not a remotely exploitable vulnerability. Requires specific kernel build parameters.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Patches available in stable kernel trees via referenced commits
Vendor Advisory: https://git.kernel.org/stable/c/14ad6ed30a10afbe91b0749d6378285f4225d482
Restart Required: Yes
Instructions:
1. Update to patched kernel version from your distribution. 2. For custom builds, apply patches from stable kernel tree. 3. Recompile and install kernel. 4. Reboot system.
🔧 Temporary Workarounds
Avoid custom MAX_SKB_FRAGS configurations
linuxUse default kernel configurations or avoid setting MAX_SKB_FRAGS to values that cause SKB_WITH_OVERHEAD(1024) < GRO_MAX_HEAD
🧯 If You Can't Patch
- Use default kernel configurations without custom MAX_SKB_FRAGS settings
- Monitor system logs for WARNING messages from netif_napi_add_weight_locked and be prepared for potential instability
🔍 How to Verify
Check if Vulnerable:
Check kernel configuration for MAX_SKB_FRAGS setting and verify if using affected kernel versions before patchesCheck Version:
uname -rVerify Fix Applied:
Check kernel version is updated beyond patched commits and verify no WARNING messages during boot related to netif_napi_add_weight_locked📡 Detection & Monitoring
Log Indicators:
- WARNING: CPU: 0 PID: 1 at net/core/dev.c:6935 netif_napi_add_weight_locked
- Kernel panic during network initialization
Network Indicators:
- Network interface initialization failures
SIEM Query:
source="kernel" AND "netif_napi_add_weight_locked" AND "WARNING"