CVE-2020-25632

Se encontró un fallo en grub2 en versiones anteriores a 2.06. La implementación de rmmod permite la descarga de un módulo usado como dependencia sin comprobar si algún otro módulo dependiente todavía está cargado, lo que conlleva a un escenario de uso de la memoria previamente liberada. Esto podría permitir una ejecución de código arbitraria o una omisión de las protecciones de Secure Boot. 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 rmmod implementation allows the unloading of a module used as a dependency without checking if any other dependent module is still loaded leading to a use-after-free scenario. This could allow arbitrary code to be executed or a bypass of Secure Boot protections. 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.