Overview
CVE-2025-54771 is a medium-severity use-after-free vulnerability identified in the GNU GRUB (Grand Unified Bootloader). This flaw can be exploited to cause a denial-of-service condition and potentially compromise data integrity or confidentiality.
Technical Details
The vulnerability stems from an incorrect memory management process within GNU GRUB’s file-closing routine. Specifically, the file-closing process fails to properly release a memory pointer, leaving an invalid reference to a file system structure. This dangling pointer can be accessed later, leading to unpredictable behavior when GRUB attempts to use the freed memory.
The core issue resides in how GRUB handles file system objects during the boot process. When a file is closed, the associated memory should be deallocated. However, due to the identified flaw, a pointer to this deallocated memory remains, creating the use-after-free condition. An attacker who can influence GRUB’s file handling (e.g., through a crafted GRUB configuration file or a malicious boot image) can trigger this vulnerability.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) score for CVE-2025-54771 is 4.9, indicating a MEDIUM severity. The CVSS vector is likely something like AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. This score reflects the following:
- Attack Vector (AV): Local (L) – An attacker needs local access to the system to exploit this vulnerability.
- Attack Complexity (AC): Low (L) – The vulnerability is relatively easy to exploit.
- Privileges Required (PR): None (N) – No privileges are required to exploit the vulnerability.
- User Interaction (UI): None (N) – No user interaction is required to exploit the vulnerability.
- Scope (S): Unchanged (U) – The vulnerability only affects the GRUB process itself.
- Confidentiality (C): None (N) – No impact to confidentiality.
- Integrity (I): None (N) – No impact to integrity.
- Availability (A): High (H) – High impact to availability (Denial of Service).
Possible Impact
The primary impact of CVE-2025-54771 is a Denial of Service (DoS). An attacker successfully exploiting this vulnerability can cause GRUB to crash, preventing the system from booting. While the CVSS score indicates no direct impact on confidentiality or integrity, it’s important to note that a successful DoS can be a precursor to more sophisticated attacks, especially if it allows an attacker to manipulate the boot process after GRUB fails.
Although confidentiality and integrity impacts are not discarded, further analysis is required to confirm the specific scenarios where those attacks are possible. A crash in the bootloader opens possibilities for attackers to potentially manipulate the system’s behavior prior to OS loading.
Mitigation and Patch Steps
The recommended mitigation is to update GNU GRUB to a patched version as soon as it becomes available. Keep an eye on security advisories from your operating system vendor for updates. Check the references below to see if patches are currently available.
General recommendations include:
- Monitor security advisories related to GRUB.
- Apply updates and patches promptly.
- Review custom GRUB configurations for any potential vulnerabilities or misconfigurations.
