A newly revealed vulnerability (CVE-2025-0690) in the GRUB2 bootloader’s read command has raised concerns about potential Secure Boot bypasses and heap memory corruption in Linux systems. Red Hat Product Security has rated this integer overflow flaw as moderately severe, as it could allow attackers with physical access and elevated privileges to execute arbitrary code or bypass Secure Boot protections.
The flaw originates in the handling of keyboard input via the GRUB2 read command. The command stores the input length in a 32-bit integer variable when processing user input. During iterative buffer reallocation, large input values can cause this integer to overflow, triggering an out-of-bounds write in a heap-based buffer. This memory corruption could destabilize GRUB’s internal data structures, potentially subverting Secure Boot’s signature verification process—critical for blocking unauthorized operating system or kernel-level malware.
Red Hat’s CVSS v3.1 score of 6.1 reflects the exploit’s constraints: it requires physical access, high privileges, and user interaction. However, successful exploitation could grant full control over the boot process, compromising confidentiality, integrity, and availability. The vulnerability links CWE-190 (Integer Overflow) to CWE-787 (Out-of-Bounds Write), enabling scenarios ranging from system crashes to arbitrary code execution.
Affected Systems and Patch Status
The vulnerability impacts:
- Red Hat Enterprise Linux (RHEL) 9 (grub2 package)
- Red Hat OpenShift Container Platform 4 (rhcos component)
- Legacy systems like RHEL 7 and 8 remain vulnerable but are no longer supported by Red Hat.
All prior package versions in affected product streams should be considered at risk until explicitly ruled out.
As of February 2025, no mitigations meeting Red Hat’s criteria for stability, scalability, and ease of use are available. Administrators should consider physical access controls until patches are released.
Secure Boot Bypass Potential
Secure Boot relies on cryptographic verification to prevent unauthorized code execution during system startup. Attackers exploiting this vulnerability could:
- Overwrite GRUB’s memory structures to load unsigned bootloaders or kernels
- Corrupt signature checks, bypassing Secure Boot protections
- Establish a persistent foothold before the operating system initializes
Although the attack complexity is high, the stakes are particularly high in environments where physical access barriers may be bypassed, such as shared or high-security systems.
Red Hat emphasizes that exploitation would likely involve multi-stage attacks, combining social engineering and privilege escalation. While CVE-2025-0690 shares similarities with the 2020 BootHole vulnerability, its reliance on physical access limits its remote exploit potential.
Mitigations
This vulnerability highlights ongoing challenges in bootloader security, including heap management complexities and the risks associated with legacy code. As GRUB2 continues evolving to support UEFI and modern hardware, these issues persist.
Researchers are urging the Linux community to accelerate development of memory-safe bootloaders, such as Rust-based alternatives, although migration timelines remain uncertain. As firmware-level attacks grow more sophisticated, this flaw underscores the need for continuous scrutiny of secure boot processes—even in established open-source projects.
