CVE-2025-0624: GRUB2 Network Boot RCE Vulnerability

CVE-2025-0624 Overview

A critical out-of-bounds write vulnerability has been discovered in GRUB2, the widely used bootloader for Linux systems. During the network boot process, when GRUB2 attempts to search for a configuration file, it copies data from a user-controlled environment variable into an internal buffer using the grub_strcpy() function. The vulnerability arises because GRUB2 fails to properly validate the length of the environment variable before allocating the internal buffer, resulting in an out-of-bounds write condition.

This vulnerability is particularly dangerous because it can be exploited to achieve remote code execution from within the same network segment where GRUB is searching for boot information. Successful exploitation could allow an attacker to bypass Secure Boot protections, fundamentally undermining the chain of trust that Secure Boot is designed to establish.

Critical Impact

Remote code execution via network boot process can bypass Secure Boot protections, compromising system integrity from the earliest stage of the boot process.

Affected Products

• GRUB2 (GNU GRand Unified Bootloader version 2)
• Red Hat Enterprise Linux systems using GRUB2
• NetApp products utilizing GRUB2 bootloader

Discovery Timeline

• February 19, 2025 - CVE-2025-0624 published to NVD
• May 21, 2025 - Last updated in NVD database

Technical Details for CVE-2025-0624

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write) and affects the network boot functionality in GRUB2. The flaw exists in the code path that handles configuration file searches during PXE or network boot operations.

When GRUB2 performs network booting, it reads environment variables to determine where to locate its configuration file. The vulnerable code path uses grub_strcpy() to copy data from these environment variables into a fixed or improperly sized internal buffer. Because grub_strcpy() does not perform bounds checking, and the allocation logic does not properly account for the actual length of the user-controlled input, an attacker can craft an oversized environment variable that causes a write beyond the allocated buffer boundaries.

The attack requires adjacent network access, meaning the attacker must be on the same network segment as the target system during the boot process. While this limits the attack surface compared to fully remote vulnerabilities, it remains highly dangerous in enterprise environments where network boot (PXE boot) is commonly used for system deployment and recovery.

Root Cause

The root cause is an improper buffer size calculation in GRUB2's network boot configuration handling code. When allocating the internal buffer for storing environment variable data, the code fails to properly measure or validate the length of the incoming data before calling grub_strcpy(). This missing bounds validation creates a classic buffer overflow condition where attacker-controlled data can overwrite adjacent memory regions.

Attack Vector

Exploitation requires an attacker positioned on the same network segment as the target system during network boot. The attack vector involves:

1. The victim system initiates a network boot (PXE boot) process
2. The attacker, positioned on the same network segment, intercepts or responds to the boot request
3. The attacker provides malicious configuration data with an oversized environment variable
4. GRUB2 attempts to copy this data using grub_strcpy() without proper bounds checking
5. The out-of-bounds write corrupts adjacent memory, potentially allowing arbitrary code execution
6. Successful exploitation executes attacker code in the pre-boot environment, bypassing Secure Boot

The vulnerability is particularly impactful because code execution at the bootloader level occurs before the operating system's security controls are initialized, and can be used to persistently compromise system integrity.

Detection Methods for CVE-2025-0624

Indicators of Compromise

• Unexpected network traffic patterns during system boot processes, particularly anomalous DHCP or TFTP responses
• Modifications to GRUB2 configuration files or boot-related environment variables
• Systems failing Secure Boot validation or exhibiting unexpected boot behavior after network boot operations
• Unusual TFTP server responses or rogue PXE servers on the network segment

Detection Strategies

• Monitor network boot environments for unauthorized DHCP or PXE servers that could serve malicious boot configurations
• Implement network segmentation to isolate PXE boot traffic from general network access
• Deploy network intrusion detection systems (NIDS) to identify anomalous boot protocol traffic
• Enable and monitor Secure Boot violation logs where available

Monitoring Recommendations

• Audit all systems that utilize network boot functionality and inventory GRUB2 versions in use
• Implement logging for PXE boot operations and review logs for unusual configuration file requests
• Monitor for firmware or bootloader integrity changes using hardware-based attestation where available
• Deploy SentinelOne Singularity Platform to monitor for post-exploitation activities that may indicate a compromised boot chain

How to Mitigate CVE-2025-0624

Immediate Actions Required

• Apply vendor-provided GRUB2 security patches immediately for all affected systems
• Restrict network access to boot infrastructure, ensuring only authorized systems can participate in PXE boot operations
• Audit network boot configurations and disable network boot functionality on systems that do not require it
• Implement VLAN segmentation for PXE boot environments to limit adjacent network attack surface

Patch Information

Multiple vendors have released security advisories and patches for this vulnerability. Red Hat has published numerous security advisories addressing this issue, including RHSA-2025:2521, RHSA-2025:2653, RHSA-2025:2655, and many others. Organizations should consult the Red Hat CVE page for CVE-2025-0624 for comprehensive patch information.

NetApp has also issued Security Advisory ntap-20250516-0006 for affected products. Additional technical details are available in Red Hat Bug Report #2346112.

Organizations should update GRUB2 packages through their distribution's package management system and ensure that Secure Boot DBX (Forbidden Signature Database) is updated to revoke vulnerable GRUB2 binaries.

Workarounds

• Disable network boot (PXE boot) functionality on systems where it is not required via BIOS/UEFI settings
• Implement strict network access controls limiting which systems can serve PXE boot configurations
• Use network segmentation to isolate boot infrastructure from untrusted network segments
• Enable Secure Boot and ensure DBX updates are applied to prevent loading of vulnerable GRUB2 binaries

# Disable PXE boot in GRUB configuration where network boot is not needed
# Check GRUB2 version to verify patch status
grub2-install --version

# Update GRUB2 packages on Red Hat-based systems
sudo dnf update grub2-common grub2-tools grub2-efi-x64

# Regenerate GRUB configuration after updates
sudo grub2-mkconfig -o /boot/grub2/grub.cfg

# Verify Secure Boot status
mokutil --sb-state