Overview
CVE-2025-61663 is a vulnerability affecting the GRUB2 bootloader. This flaw is classified as a Use-after-Free vulnerability within the ‘normal’ command. If exploited, it allows an attacker with the ability to execute the ‘normal’ command to trigger a Denial of Service (DoS) condition, potentially leading to system instability and a complete crash.
Technical Details
The core of the vulnerability lies in the improper unregistration of the ‘normal’ command when the corresponding module is unloaded. This leads to a Use-after-Free scenario. When the system attempts to access the ‘normal’ command after the module is unloaded, it accesses memory that is no longer valid, causing a crash.
Specifically, the ‘normal’ command in GRUB2 is not correctly unregistered upon module unloading. This allows an attacker capable of executing the ‘normal’ command to force the system to access memory locations that have been freed. This memory access results in undefined behavior, ultimately leading to a system crash.
CVSS Analysis
The Common Vulnerability Scoring System (CVSS) provides a standardized way to assess the severity of vulnerabilities. CVE-2025-61663 has a CVSS score of 4.9 (Medium).
- Base Score: 4.9
- Vector: (We are not able to determine full vector based on description)
- Severity: Medium
This score reflects the relatively low attack complexity, but potentially high impact on system availability.
Possible Impact
The exploitation of CVE-2025-61663 can have significant consequences:
- Denial of Service (DoS): The most immediate impact is a system crash, rendering the affected system unavailable.
- System Instability: Even if the system doesn’t crash immediately, the memory corruption can lead to unpredictable behavior and instability.
- Data Integrity and Confidentiality: The potential impact to data integrity and confidentiality is also not discarded, even though the primary issue is availability.
Mitigation and Patch Steps
The primary mitigation strategy is to apply the official patch released by the GRUB2 maintainers. Contact your operating system vendor for specific instructions on updating GRUB2.
- Check for Updates: Regularly check for and install security updates from your operating system vendor.
- Apply Patches: Ensure that the GRUB2 package is updated to a version that addresses CVE-2025-61663.
- Monitor Systems: Closely monitor systems for any signs of instability or crashes that might indicate exploitation.
