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Rewterz Threat Advisory – CVE-2019-6974 – Linux Kernel KVM “kvm_ioctl_create_device()” Use-AfterFree Vulnerability

Severity

Medium

Analysis Summary


 A use-after-free vulnerability was found in the way the Linux kernel’s KVM hypervisor implements its device control API. While creating a device via kvm_ioctl_create_device(), the device holds a reference to a VM object, later this reference is transferred to the caller’s file descriptor table. If such file descriptor was to be closed, reference count to the VM object could become zero, potentially leading to a use-after-free issue. A user/process could use this flaw to crash the guest VM resulting in a denial of service issue or, potentially, gain privileged access to a system.

Impact

Denial of service

Privilege escalation

System access

Affected Products

  • Linux Kernel 3.16.x
  • Linux Kernel 4.4.x
  • Linux Kernel 4.9.x
  • Linux Kernel 4.14.x
  • Linux Kernel 4.19.x
  • Linux Kernel 4.20.x

Remediation

Update to a fixed version if available.

Versions 4.20.x:

Update to version 4.20.8.

Versions 4.19.x:

Update to version 4.19.21.

Versions 4.14.x:

Update to version 4.14.99.

Versions 4.9.x:

Update to version 4.9.156.

Versions 4.4.x:

Update to version 4.4.176.