CVE-2025-0689: 
Linux Debian vulnerability analysis and mitigation

CVE-2025-0689 is a security vulnerability discovered in GRUB's UDF filesystem module. The vulnerability was disclosed on February 18, 2025, and affects the GRUB bootloader system. When reading data from disk, the module utilizes user-controlled data length metadata to allocate internal buffers. The issue arises when iterating through disk sectors, where the system incorrectly assumes the read size from the disk is always smaller than the allocated buffer size (GRUB Devel).

The vulnerability is classified as a heap-based buffer overflow in the grubudfread_block() function. The issue occurs due to improper validation of buffer sizes when reading disk sectors. The vulnerability has been assigned a CVSS v3.1 Base Score of 6.4 (MEDIUM) with the vector string CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H, indicating local access required, high attack complexity, high privileges required, and potential for high impact on confidentiality, integrity, and availability (Red Hat CVE).

A successful exploitation of this vulnerability could lead to heap-based buffer overflow, resulting in critical data corruption. The most severe consequence is the potential for arbitrary code execution that could bypass secure boot protections. This poses a significant security risk as it could allow attackers to compromise the boot process integrity (NVD).

Fixes for this vulnerability have been made public and incorporated into updated versions of GRUB. A new upstream shim release is expected that will publish updated Sbat (Secure Boot Advanced Targeting) revocations to allow older GRUB versions to be revoked. For complete mitigation, systems should be updated with the latest GRUB version and corresponding shim updates (GRUB Devel).