CVE-2025-0677: 
Linux Debian vulnerability analysis and mitigation

A critical vulnerability (CVE-2025-0677) was discovered in GRUB2's UFS module, disclosed on February 18, 2025. The flaw affects the symlink lookup functionality where the module fails to properly validate symlink data size overflow conditions. This vulnerability impacts various Linux distributions including Debian and Ubuntu systems (Debian Tracker, Ubuntu Security).

The vulnerability occurs during symlink lookup in GRUB's UFS module. When checking the inode's data size to allocate an internal buffer for file content reading, the module fails to verify if the symlink data size has overflown. This oversight results in grubmalloc() being called with an insufficient size parameter. Subsequently, when reading data from disk into the buffer, the grubufslookupsymlink() function writes beyond the allocated buffer size. The vulnerability has been assigned a CVSS v3.1 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 (OSS Security).

The vulnerability can be exploited by crafting a malicious filesystem, leading to heap corruption through out-of-bounds writes. This could potentially result in arbitrary code execution, which could be leveraged to bypass secure boot mechanisms. The impact is particularly severe as it affects system security at the bootloader level (Debian Tracker).

Fixed versions have been released for various distributions. Debian has addressed the vulnerability in version 2.12-7 for the unstable (sid) release. Other distributions are actively working on patches. Users are advised to update their GRUB2 packages as soon as fixes become available (Debian Tracker).