CVE-2025-21659
📋 TL;DR
This Linux kernel vulnerability allows unauthorized access to NAPI (New API) instances across network namespaces, potentially enabling information disclosure or disruption of network operations. It affects Linux systems using kernel versions with the vulnerable netlink API implementation. Attackers could exploit this to interfere with network processing in multi-tenant or containerized environments.
💻 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 →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
An attacker could disrupt network operations across namespaces, cause denial of service, or potentially access sensitive network state information from other containers/namespaces.
Likely Case
Information disclosure about network state across namespaces, potentially enabling further attacks or disrupting network performance in containerized environments.
If Mitigated
Minimal impact with proper namespace isolation and network segmentation in place.
🎯 Exploit Status
Requires local access and ability to interact with netlink API; exploitation likely requires understanding of kernel internals.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Kernel versions containing commits b683ba0df11ff563cc237eb1b74d6adfa77226bf and d1cacd74776895f6435941f86a1130e58f6dd226
Vendor Advisory: https://git.kernel.org/stable/c/b683ba0df11ff563cc237eb1b74d6adfa77226bf
Restart Required: Yes
Instructions:
1. Update Linux kernel to version containing the fixes. 2. Check with your distribution vendor for specific patched kernel versions. 3. Reboot system after kernel update.
🔧 Temporary Workarounds
Restrict netlink access
linuxLimit which users/processes can access netlink sockets to reduce attack surface
# Use Linux capabilities or SELinux/AppArmor to restrict netlink access
# Example: setcap -r /path/to/binary (remove capabilities)
Network namespace hardening
linuxImplement strict namespace isolation and limit container privileges
# Run containers with minimal privileges:
docker run --cap-drop=ALL --cap-add=NET_ADMIN ...
# Or use user namespaces:
docker run --userns=host ...
🧯 If You Can't Patch
- Implement strict network namespace isolation and limit container-to-container communication
- Use security modules (SELinux/AppArmor) to restrict netlink socket access
🔍 How to Verify
Check if Vulnerable:
Check kernel version and verify if it contains the vulnerable code by examining kernel source or checking with distribution vendorCheck Version:
uname -rVerify Fix Applied:
Verify kernel version contains the fix commits: b683ba0df11ff563cc237eb1b74d6adfa77226bf and d1cacd74776895f6435941f86a1130e58f6dd226📡 Detection & Monitoring
Log Indicators:
- Unusual netlink socket activity
- Failed namespace boundary checks in kernel logs
- Unexpected cross-namespace network operations
Network Indicators:
- Abnormal network behavior across namespaces
- Unexpected network state changes
SIEM Query:
kernel: "napi_by_id" OR "netlink" AND ("namespace" OR "boundary")