A critical set of 20 vulnerabilities in GRUB2, the ubiquitous bootloader underpinning most Linux distributions and Unix-like systems, has exposed millions of devices to potential secure boot bypass, remote code execution, and persistent firmware-level attacks.
These flaws (CVSS scores up to 7.5) span heap overflows, integer overflows, and use-after-free errors across filesystem drivers, network stacks, and cryptographic modules.
GRUB2 Vulnerabilities
Attack vectors include malformed filesystems (CVE-2025-0677, CVE-2025-0685), crafted JPEG images (CVE-2024-45774), and network boot configurations (CVE-2025-0624).
For instance, CVE-2025-0624 enables remote code execution via DHCP server responses during network booting, allowing attackers within the same network segment to inject malicious payloads into pre-boot memory.
Integer overflow chains proved particularly dangerous. The Squash4 driver (CVE-2025-0678) and JFS module (CVE-2025-0685) fail to validate buffer sizes derived from filesystem metadata, leading to heap-based out-of-bounds writes during file reads.
Similarly, the UDF filesystem driver (CVE-2025-0689) permits arbitrary code execution via unvalidated sector counts during disk reads.
The vulnerabilities, discovered during a proactive code audit led by Daniel Kiper and security researchers from Red Hat, Oracle, and SUSE, exploit GRUB2’s role as the first software layer executed during system startup.
Five vulnerabilities directly threaten UEFI Secure Boot integrity. CVE-2025-0622’s use-after-free in the GPG module allows persistent hook execution after module unloading, while CVE-2025-1118’s unsecured memory dump command leaks cryptographic secrets from lockdown mode.
“These flaws weaponize GRUB2’s privileged position in the trust chain,” warned Jonathan Bar Or, who reported six CVEs. Attackers could overwrite boot measurements in TPM registers or modify kernel command lines to disable security policies.
Mitigation Measures
Mitigation requires coordinated updates to GRUB2, shim (v25+), and SBAT metadata a revocation framework replacing traditional UEFI dbx lists.
Vendors must rebuild boot artifacts with SBAT generation 5+ to enforce component-level blacklisting. However, legacy systems using unsigned GRUB modules or custom Secure Boot keys remain vulnerable.
Red Hat’s advisory (RHSA-2024:2456) highlights ongoing risks, noting that CVE-2023-4692 (NTFS OOB write) and CVE-2024-1048 (bootflag abuse) persist in unpatched RHEL 9 systems.
Canonical’s discourse thread confirms similar threats to Ubuntu’s Secure Boot implementation, including CVE-2020-27779’s memory region manipulation via the cutmem command.
As attackers increasingly target low-level components, this disclosure underscores the fragility of hardware-rooted trust models.
With GRUB2 installed on over 72% of Linux systems, the window of vulnerability remains a critical concern for enterprise and government infrastructures worldwide.
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