GRUB2 Under Attack: Unveiling CVE-2025-54770 – A Network Module DoS Vulnerability

Published: 2025-11-18T19:15:49.200

Overview

A critical vulnerability, identified as CVE-2025-54770, has been discovered in the GRUB2 bootloader’s network module. This flaw presents a Denial of Service (DoS) risk, potentially leading to system instability and downtime. This article provides a comprehensive analysis of the vulnerability, its potential impact, and recommended mitigation strategies.

Technical Details

CVE-2025-54770 is a Use-after-Free vulnerability originating from the improper handling of the net_set_vlan command within GRUB2’s network module. Specifically, the net_set_vlan command is not correctly unregistered when the network module is unloaded. This oversight allows an attacker, with the ability to execute this command, to trigger a scenario where the system attempts to access memory locations that are no longer valid.

The vulnerability resides in the cleanup process when the network module is unloaded. The lack of proper unregistration of the net_set_vlan command leaves a dangling pointer, which, when dereferenced after the module has been unloaded, causes a Use-after-Free condition.

CVSS Analysis

• Severity: MEDIUM
• CVSS Score: 4.9

The CVSS score of 4.9 indicates a medium severity vulnerability. While exploitation requires the ability to execute commands within the GRUB2 environment, the resulting Denial of Service can significantly impact system availability. The vector is local, requiring either physical access or pre-existing privileged access to the system.

Possible Impact

Successful exploitation of CVE-2025-54770 can lead to the following consequences:

• System Instability: Accessing invalid memory locations can cause unpredictable behavior.
• Denial of Service (DoS): The system may crash completely, halting all operations and rendering it unavailable.
• Boot Failure: In severe cases, the system might fail to boot properly, requiring intervention to restore functionality.

Mitigation and Patch Steps

The recommended mitigation strategy is to apply the official patch released by your operating system vendor. Contact your vendor for the most up-to-date instructions and packages.

Here’s a general outline of the steps to take:

1. Check for Updates: Use your system’s package manager (e.g., apt on Debian/Ubuntu, yum on CentOS/RHEL, pacman on Arch Linux) to check for available updates for the grub2 package.
2. Apply Updates: Install any available updates for grub2. The updated package should include the fix for CVE-2025-54770.
3. Reboot: After applying the updates, reboot your system to ensure the new GRUB2 version is loaded and active.
4. Verify: After rebooting, verify that the patched GRUB2 version is running. Consult your operating system’s documentation for specific commands to check the GRUB2 version.

Workaround (If a Patch is Not Immediately Available): As a temporary workaround, restrict access to the GRUB2 command line to prevent unauthorized execution of the net_set_vlan command. This can be achieved through password protecting GRUB2. However, this is not a complete solution and applying the official patch is strongly recommended.

References

• Red Hat CVE Page: CVE-2025-54770
• Red Hat Bugzilla: 2413813