CVE-2021-47062: linux kernel Null Dereference — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Use online_vcpus, not created_vcpus, to iterate over vCPUs Use the kvm_for_each_vcpu() helper to iterate over vCPUs when encrypting VMSAs for SEV, which effectively switches to use online_vcpus instead of created_vcpus. This fixes a possible null-pointer dereference as created_vcpus does not guarantee a vCPU exists, since it is updated at the very beginning of KVM_CREATE_VCPU. created_vcpus exists to allow the bulk of vCPU creation to run in parallel, while still correctly restricting the max number of max vCPUs.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.11 — 5.11.21
linux	linux_kernel	5.12 — 5.12.4

References

Advisories & Patches

https://git.kernel.org/stable/c/ba7bf5d6336aa9c0d977b161bfa420c56d46ee40 https://git.kernel.org/stable/c/bd0cced2ae93195668f983d443f7f17e8efd24d2 https://git.kernel.org/stable/c/c36b16d29f3af5f32fc1b2a3401bf48f71cabee1 https://git.kernel.org/stable/c/ba7bf5d6336aa9c0d977b161bfa420c56d46ee40 https://git.kernel.org/stable/c/bd0cced2ae93195668f983d443f7f17e8efd24d2 https://git.kernel.org/stable/c/c36b16d29f3af5f32fc1b2a3401bf48f71cabee1

Frequently Asked Questions

What is CVE-2021-47062? +

In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Use online_vcpus, not created_vcpus, to iterate over vCPUs Use the kvm_for_each_vcpu() helper to iterate over vCPUs when encrypting VMSAs for SEV, which effectively switches to use online_vcpus instead of created_vcpus. This fixes a possible null-pointer dereference as created_vcpus does not guarantee a vCPU exists, since it is updated at the very beginning of KVM_CREATE_VCPU. created_vcpus exists to allow the bulk of vCPU creation to run in parallel, while still correctly restricting the max number of max vCPUs. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47062? +

CVE-2021-47062 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2021-47062? +

CVE-2021-47062 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2021-47062? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2021-47062