CVE-2021-20233

Se encontró un fallo en grub2 en versiones anteriores a 2.06. La función Setparam_prefix() en el código de renderización del menú lleva a cabo un cálculo de longitud asumiendo que expresar una comilla simple entre comillas requerirá 3 caracteres, mientras que actualmente requiere 4 caracteres, lo que permite a un atacante corromper la memoria por un byte para cada comilla en la entrada. La mayor amenaza de esta vulnerabilidad es la confidencialidad e integridad de los datos, así como la disponibilidad del sistema

A flaw was found in grub2. Setparam_prefix() in the menu rendering code performs a length calculation on the assumption that expressing a quoted single quote will require 3 characters, while it actually requires 4 characters which allows an attacker to corrupt memory by one byte for each quote in the input. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.

Máté Kukri discovered that the acpi command in GRUB 2 allowed privileged users to load crafted ACPI tables when secure boot is enabled. An attacker could use this to bypass UEFI Secure Boot restrictions. Chris Coulson discovered that the rmmod command in GRUB 2 contained a use- after-free vulnerability. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions. Chris Coulson discovered that a buffer overflow existed in the command line parser in GRUB 2. A local attacker could use this to execute arbitrary code and bypass UEFI Secure Boot restrictions. Various other issues were also addressed.