CVE-2025-1118: GRUB2 Information Disclosure Vulnerability

CVE-2025-1118 Overview

A security flaw was discovered in GRUB2, the widely-used bootloader for Linux systems. The vulnerability exists because GRUB2's dump command is not blocked when the bootloader is operating in lockdown mode. This oversight allows an attacker with local access and high privileges to read arbitrary memory contents, potentially extracting sensitive information such as cryptographic signatures, salts, and other security-critical data from system memory.

Critical Impact

Attackers with local access can bypass GRUB2 lockdown protections to extract sensitive cryptographic material and signatures from memory, potentially compromising system security and Secure Boot integrity.

Affected Products

• GRUB2 (GNU GRand Unified Bootloader 2)
• Linux systems utilizing GRUB2 with lockdown mode enabled
• Systems relying on Secure Boot with GRUB2

Discovery Timeline

• 2025-02-19 - CVE-2025-1118 published to NVD
• 2025-09-18 - Last updated in NVD database

Technical Details for CVE-2025-1118

Vulnerability Analysis

This vulnerability is classified under CWE-501 (Trust Boundary Violation). The core issue stems from an incomplete implementation of GRUB2's lockdown mode security controls. Lockdown mode is designed to prevent unauthorized access to sensitive bootloader functionality when Secure Boot is enabled, ensuring the boot process integrity cannot be tampered with by privileged local users.

However, the dump command—which provides raw memory read capabilities—was not included in the list of restricted commands during lockdown mode. This creates a trust boundary violation where functionality that should be inaccessible in a security-hardened state remains available, enabling memory disclosure attacks.

The attack requires local access with high privileges (such as root or physical console access), but in scenarios where lockdown mode is specifically deployed to prevent privileged users from tampering with boot security, this bypass undermines the intended security model.

Root Cause

The root cause is an incomplete security control implementation in GRUB2's lockdown mode command filtering. When lockdown mode is engaged, GRUB2 is supposed to disable commands that could compromise system security or allow extraction of sensitive data. The dump command, which provides direct memory access capabilities, was inadvertently omitted from the lockdown command blacklist, creating a path for memory information disclosure.

Attack Vector

The attack vector is local, requiring an attacker to have high-privilege access to the GRUB2 command line interface. In a typical exploitation scenario:

1. An attacker gains access to the GRUB2 command prompt during system boot or through console access
2. Despite lockdown mode being active, the attacker executes the dump command
3. The attacker reads arbitrary memory regions to extract sensitive data
4. Extracted information may include cryptographic signatures, salts, encryption keys, or other security-sensitive material stored in memory

This vulnerability is particularly concerning in environments where lockdown mode is deployed as a defense-in-depth measure against insider threats or to maintain Secure Boot chain integrity even when privileged access is compromised.

Detection Methods for CVE-2025-1118

Indicators of Compromise

• Unexpected access to GRUB2 command line during boot process
• Evidence of the dump command being executed in GRUB2 logs or boot records
• Unauthorized physical or console access to systems during boot sequence
• Anomalous boot timing or interrupted boot processes suggesting manual intervention

Detection Strategies

• Monitor for unauthorized physical access to systems during boot procedures
• Implement boot logging and audit trails where possible to detect command-line access
• Review system access logs for evidence of console or remote management access during boot windows
• Deploy hardware security modules or TPM-based attestation to detect boot process tampering

Monitoring Recommendations

• Enable and review UEFI/BIOS boot logs for signs of manual boot interruption
• Implement physical security controls to limit access during system startup
• Configure remote management interfaces (IPMI, iLO, iDRAC) with strong authentication and audit logging
• Consider implementing measured boot with TPM attestation to detect boot process anomalies

How to Mitigate CVE-2025-1118

Immediate Actions Required

• Apply the latest GRUB2 security patches from your Linux distribution vendor
• Review Red Hat Security Errata RHSA-2025:16154 for patch details
• Restrict physical and console access to systems during boot procedures
• Audit remote management access to ensure only authorized personnel can access boot interfaces
• Consider implementing additional boot security measures such as BIOS/UEFI passwords

Patch Information

Red Hat has released security updates addressing this vulnerability. Organizations running RHEL and derivative distributions should consult the Red Hat Security Errata RHSA-2025:16154 for specific package versions and update instructions. Additional details are available through Red Hat CVE Details and Red Hat Bug Report #2346137.

After updating GRUB2 packages, regenerate the GRUB2 configuration and reinstall the bootloader to ensure the patched version is active.

Workarounds

• Implement strict physical security controls to prevent unauthorized access during boot
• Configure BIOS/UEFI passwords to prevent unauthorized access to boot options
• Disable remote management interfaces when not actively needed for administration
• Use boot media integrity verification mechanisms where available
• Consider deploying full disk encryption with pre-boot authentication to add defense layers

# After applying GRUB2 security updates, regenerate configuration
# For RHEL/CentOS/Fedora systems:
grub2-mkconfig -o /boot/grub2/grub.cfg

# For Debian/Ubuntu systems:
update-grub

# Verify the updated GRUB2 version is installed
grub2-install --version