CVE-2018-10853

Se ha encontrado un error en la forma en la que el hipervisor KVM del kernel de Linux en versiones anteriores a la 4.18 emulaba instrucciones como sgdt/sidt/fxsave/fxrstor. No comprobó el nivel de privilegios actual (CPL) al emular instrucciones sin privilegios. Un usuario invitado o un proceso sin privilegios podrían emplear este error para escalar sus privilegios en el invitado.

A flaw was found in the way Linux kernel KVM hypervisor emulated instructions such as sgdt/sidt/fxsave/fxrstor. It did not check current privilege(CPL) level while emulating unprivileged instructions. An unprivileged guest user/process could use this flaw to potentially escalate privileges inside guest.

Jann Horn discovered that the vmacache subsystem did not properly handle sequence number overflows, leading to a use-after-free vulnerability. A local attacker could use this to cause a denial of service or execute arbitrary code. It was discovered that the paravirtualization implementation in the Linux kernel did not properly handle some indirect calls, reducing the effectiveness of Spectre v2 mitigations for paravirtual guests. A local attacker could use this to expose sensitive information. Various other issues were also addressed.