CVE-2020-27779

Se encontró un fallo en grub2 en versiones anteriores a 2.06. El comando cutmem no respeta el bloqueo de secure boot, permitiendo a un atacante privilegiado eliminar rangos de direcciones de la memoria, creando una oportunidad para omitir unas protecciones de SecureBoot después de una clasificación apropiada sobre el diseño de la memoria de grub. 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. The cutmem command does not honor secure boot locking allowing an privileged attacker to remove address ranges from memory creating an opportunity to circumvent SecureBoot protections after proper triage about grub's memory layout. 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.