A critical vulnerability has been discovered in the Linux kernel and assigned CVE-2025-21659. This vulnerability affects the Network API (NAPI) within the kernel, allowing unauthorized access to NAPI instances from different namespaces. In this article, we will take an in-depth look at this vulnerability, the code changes made to address it, and the steps you should take to protect your systems.
Vulnerability Details
The vulnerability stems from the fact that NAPI IDs were not fully exposed to user space prior to the netlink API, so they were never namespaced. As a result, malicious actors could potentially exploit this vulnerability to access NAPI instances belonging to another namespace, which could lead to information leakage, unauthorized network communication, or even full system compromise.
The issue has been addressed within the Linux kernel by ensuring that, at the very least, NAPI instances belong to the same netns (network namespace) as the owner of the genl sock (Generic Netlink socket). This change prevents attackers from gaining unauthorized access to NAPI instances from another namespace.
Here's the code snippet that shows the modification
// net/core/dev.c
static struct napi_struct *napi_by_id(struct net *net, int ifindex)
{
struct net_device *dev;
dev = dev_get_by_napi_id(net, ifindex);
if (!dev)
return NULL;
dev_put(dev);
return &dev->napi;
}
The napi_by_id() function has been made static and moved, now ensuring that the NAPI instances are properly namespaced and protected.
Original References
To get more details about the vulnerability and the full patch, please refer to the following sources:
- Linux Kernel Commit
- CVE List Entry for CVE-2025-21659
- Kernel.org Advisory
Exploit Details
As of the time of writing this article, there have been no reports of this vulnerability being actively exploited in the wild. However, it is important to remain vigilant and take proactive measures to protect your systems.
Remediation
To fully protect your Linux systems from this vulnerability, you need to update your kernel to a version containing the patch. This might require you to compile and install a new kernel, especially if your system is running a custom or an older version of the kernel.
Stay informed about the latest security vulnerabilities discovered in the Linux kernel by periodically visiting the kernel.org website or subscribing to their mailing list.
Conclusion
CVE-2025-21659 is a critical vulnerability in the Linux kernel that could potentially lead to unauthorized access to NAPI instances from another namespace. By updating your Linux kernel to a version containing the patch addressing this issue, you can maintain the security and stability of your systems.
Timeline
Published on: 01/21/2025 13:15:09 UTC