Grub2: read: integer overflow may lead to out-of-bounds write

A flaw was found in systems utilizing LUKS-encrypted disks with GRUB configured for TPM-based auto-decryption. When GRUB is set to automatically decrypt disks using keys stored in the TPM, it reads the decryption key into system memory. If an attacker with physical access can corrupt the underlying filesystem superblock, GRUB will fail to locate a valid filesystem and enter rescue mode. At this point, the disk is already decrypted, and the decryption key remains loaded in system memory. This scenario may allow an attacker with physical access to access the unencrypted data without any further authentication, thereby compromising data confidentiality. Furthermore, the ability to force this state through filesystem corruption also presents a data integrity concern.

A flaw was found in grub2. When performing a symlink lookup, the grub's UFS module checks the inode's data size to allocate the internal buffer to read the file content, however, it fails to check if the symlink data size has overflown. When this occurs, grubmalloc() may be called with a smaller value than needed. When further reading the data from the disk into the buffer, the grubufslookupsymlink() function will write past the end of the allocated size. An attack can leverage this by crafting a malicious filesystem, and as a result, it will corrupt data stored in the heap, allowing for arbitrary code execution used to by-pass secure boot mechanisms.

When reading tar files, grub2 allocates an internal buffer for the file name however it fails to properly verify the allocation against possible Integer Overflows. It's possible to cause the allocation length to overflow with a crafted tar file leading to a head Out-of-bounds write, as consequence an attacker may leverage this to eventually circumvent secure boot protections.

When reading language .mo file in grubmofileopen(), grub2 fails to verify to a integer overflow when allocating its internal buffer. A crafted .mo file may lead to the buffer size calculation to overflow leading to Out-of-bound reads and writes. An attacker may leverage this flaw to leak sensitive data or overwrite critical data possibly leading to the circumvention of secure boot protections.