CVE-2021-47670: Linux Kernel Vulnerability Threatens System Compromise

Overview

In our digital era, the security of the Linux kernel is of paramount importance due to its widespread usage by businesses and individuals alike. A newly discovered vulnerability, known as CVE-2021-47670, threatens this security. This vulnerability could potentially lead to system compromise or data leakage, making it a significant concern for all Linux users.
This blog post aims to provide an in-depth understanding of CVE-2021-47670, its potential impact, and how it can be mitigated. The vulnerability primarily affects the Linux kernel and arises from a use-after-free bug in the peak_usb module.

Vulnerability Summary

CVE ID: CVE-2021-47670
Severity: High (7.8 CVSS score)
Attack Vector: Local
Privileges Required: Low
User Interaction: None
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

Linux Kernel | Up to 5.13.19

How the Exploit Works

The vulnerability arises from the unsafe dereferencing of the socket buffer (skb) after calling peak_usb_netif_rx_ni(skb). Specifically, the can_frame cf, which aliases the skb memory is accessed after the peak_usb_netif_rx_ni(). This leads to a use-after-free condition, which can then be exploited to execute arbitrary code or cause a denial of service.

Conceptual Example Code

While the exact exploit code may differ based on the specific circumstances, the following is a conceptual example in pseudocode of how the vulnerability might be exploited:

// Allocate socket buffer
struct sk_buff *skb = alloc_skb(...);
// Fill the buffer with data
...
// Call peak_usb_netif_rx_ni(), which frees the socket buffer
peak_usb_netif_rx_ni(skb);
// Access the freed buffer, leading to a use-after-free condition
struct can_frame *cf = (struct can_frame *)skb->data;

Note: This example is for illustrative purposes only and does not represent a working exploit.

Mitigation Guidance

The recommended mitigation for this vulnerability is to apply the vendor-provided patch. This will resolve the vulnerability by reordering the lines involved in the issue. However, as a temporary mitigation, using a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) can also help to detect and prevent exploitation attempts.