Denial of service in Linux kernel KVM

1) NULL pointer dereference

EUVDB-ID: #VU59895

Risk: Low

CVSSv3.1: 4.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-4095

CWE-ID: CWE-476 - NULL Pointer Dereference

Exploit availability: No

Description

The vulnerability allows a local user to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error within the Linux kernel's KVM when dirty ring logging is enabled without an active vCPU context in kvm_dirty_ring_get() function in virt/kvm/dirty_ring.c. A local user can pass specially crafted input to the KVM_XEN_HVM_SET_ATTR IOCTL and perform a denial of service (DoS) attack.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Linux kernel: All versions

External links

http://bugzilla.redhat.com/show_bug.cgi?id=2031194
http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=55749769fe608fa3f4a075e42e89d237c8e37637

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.