CVE-2021-47255: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: kvm: LAPIC: Restore guard to prevent illegal APIC register access Per the SDM, "any access that touches bytes 4 through 15 of an APIC register may cause undefined behavior and must not be executed." Worse, such an access in kvm_lapic_reg_read can result in a leak of kernel stack contents. Prior to commit 01402cf81051 ("kvm: LAPIC: write down valid APIC registers"), such an access was explicitly disallowed. Restore the guard that was removed in that commit.

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CVSS v3.1 Score

7.1

HIGH

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

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.3 — 5.4.128
linux	linux_kernel	5.5 — 5.10.46
linux	linux_kernel	5.11 — 5.12.13
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/018685461a5b9a9a70e664ac77aef0d7415a3fd5 https://git.kernel.org/stable/c/218bf772bddd221489c38dde6ef8e917131161f6 https://git.kernel.org/stable/c/a2aff09807fbe4018c269d3773a629949058b210 https://git.kernel.org/stable/c/bf99ea52970caeb4583bdba1192c1f9b53b12c84 https://git.kernel.org/stable/c/018685461a5b9a9a70e664ac77aef0d7415a3fd5 https://git.kernel.org/stable/c/218bf772bddd221489c38dde6ef8e917131161f6 https://git.kernel.org/stable/c/a2aff09807fbe4018c269d3773a629949058b210 https://git.kernel.org/stable/c/bf99ea52970caeb4583bdba1192c1f9b53b12c84

Frequently Asked Questions

What is CVE-2021-47255? +

In the Linux kernel, the following vulnerability has been resolved: kvm: LAPIC: Restore guard to prevent illegal APIC register access Per the SDM, "any access that touches bytes 4 through 15 of an APIC register may cause undefined behavior and must not be executed." Worse, such an access in kvm_lapic_reg_read can result in a leak of kernel stack contents. Prior to commit 01402cf81051 ("kvm: LAPIC: write down valid APIC registers"), such an access was explicitly disallowed. Restore the guard that was removed in that commit. It has a CVSS v3.1 base score of 7.1 (HIGH).

How severe is CVE-2021-47255? +

CVE-2021-47255 has a CVSS v3.1 score of 7.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2021-47255? +

CVE-2021-47255 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-2021-47255? +

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-2021-47255