CVE-2023-4949 in Grub-Legacy
Summary
by MITRE • 11/10/2023
An attacker with local access to a system (either through a disk or external drive) can present a modified XFS partition to grub-legacy in such a way to exploit a memory corruption in grub’s XFS file system implementation.
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Analysis
by VulDB Data Team • 12/06/2023
This vulnerability resides in the grub-legacy bootloader's implementation of XFS file system handling, representing a critical security flaw that leverages local system access to achieve memory corruption. The issue manifests when an attacker with physical access to a system can manipulate XFS partitions through external storage devices, creating a modified partition structure that triggers a flaw in grub's XFS parsing code. This represents a sophisticated attack vector that combines physical access exploitation with bootloader-level memory corruption, making it particularly dangerous in environments where unauthorized physical access is possible.
The technical flaw stems from inadequate input validation and memory management within grub-legacy's XFS file system parser. When the bootloader attempts to read and interpret modified XFS partition structures, it fails to properly validate the partition metadata, leading to buffer overflows or memory corruption issues. This memory corruption can result in arbitrary code execution or system instability, as the bootloader's XFS implementation does not properly handle malformed or maliciously crafted partition data. The vulnerability specifically affects the legacy grub bootloader implementation and demonstrates poor adherence to secure coding practices regarding memory allocation and bounds checking.
The operational impact of this vulnerability extends beyond simple system compromise, as it represents a potential escalation path for attackers who have already gained physical access to target systems. Attackers can leverage this flaw to bypass normal system boot processes and potentially gain root-level access or execute malicious payloads during the boot sequence. The attack requires local access and the ability to modify storage media, but once successful, it can provide persistent access to the target system. This vulnerability affects systems running grub-legacy and represents a significant risk in environments where physical security controls are inadequate or where removable media is permitted.
Mitigation strategies should focus on immediate remediation through upgrading to modern bootloader implementations such as grub2, which contains improved XFS handling and memory protection mechanisms. Organizations should also implement strict physical access controls to prevent unauthorized modification of storage devices and enforce secure boot policies that validate bootloader integrity. The vulnerability aligns with CWE-121 for buffer overflow conditions and relates to ATT&CK technique T1542.001 for bootkit creation and T1068 for local privilege escalation. Regular security audits of bootloaders and system firmware should be conducted to identify similar memory corruption vulnerabilities in legacy components, particularly in environments where older system configurations persist due to compatibility requirements.