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NVD / CVE Program· CNA Linux

CVE-2021-47008: KVM: SVM: Make sure GHCB is mapped before updating

Noroxi assessment

Priority: Monitor (action score 22/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.23% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux a3ba26ecfb569f4aa3f867e80c02aa65f20aadad, fb9e14f4f8217a0980f8da2c8ff70dee058cbe47, fd722a57fe0b80133dacae4e1c852ee4212f9b2e.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux a3ba26ecfb569f4aa3f867e80c02aa65f20aadad, fb9e14f4f8217a0980f8da2c8ff70dee058cbe47, fd722a57fe0b80133dacae4e1c852ee4212f9b2e or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Make sure GHCB is mapped before updating Access to the GHCB is mainly in the VMGEXIT path and it is known that the GHCB will be mapped. But there are two paths where it is possible the GHCB might not be mapped. The sev_vcpu_deliver_sipi_vector() routine will update the GHCB to inform the caller of the AP Reset Hold NAE event that a SIPI has been delivered. However, if a SIPI is performed without a corresponding AP Reset Hold, then the GHCB might not be mapped (depending on the previous VMEXIT), which will result in a NULL pointer dereference. The svm_complete_emulated_msr() routine will update the GHCB to inform the caller of a RDMSR/WRMSR operation about any errors. While it is likely that the GHCB will be mapped in this situation, add a safe guard in this path to be certain a NULL pointer dereference is not encountered.

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
Feb 28, 2024
Updated
Jun 17, 2026
EPSS
0.2% · 14th percentile

Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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When you'll hear from us

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  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel5.11 and later · before 5.11.22
  • linux linux kernel5.12 and later · before 5.12.5

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.11affected
    • f1c6366e304328de301be362eca905a3503ff33b and later · before fb9e14f4f8217a0980f8da2c8ff70dee058cbe47affected · git
    • f1c6366e304328de301be362eca905a3503ff33b and later · before fd722a57fe0b80133dacae4e1c852ee4212f9b2eaffected · git
    • f1c6366e304328de301be362eca905a3503ff33b and later · before a3ba26ecfb569f4aa3f867e80c02aa65f20aadadaffected · git
    • before 5.11not affected · semver
    • 5.11.22 and later · up to and including 5.11.*not affected · semver
    • 5.12.5 and later · up to and including 5.12.*not affected · semver
    • 5.13 and laternot affected · original_commit_for_fix

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2021-47006Feb 28, 2024 · ARM: 9064/1: hw_breakpoint: Do not directly check the event's overflow_handler hook
    22Monitor
  • ← EarlierCVE-2021-47007Feb 28, 2024 · f2fs: fix panic during f2fs_resize_fs()
    22Monitor
  • Later →CVE-2021-47009Feb 28, 2024 · KEYS: trusted: Fix memory leak on object td
    22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linuxa3ba26ecfb569f4aa3f867e80c02aa65f20aadadVendor (CNA)
Linux Linuxfb9e14f4f8217a0980f8da2c8ff70dee058cbe47Vendor (CNA)
Linux Linuxfd722a57fe0b80133dacae4e1c852ee4212f9b2eVendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-476 · NULL Pointer Dereference

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (2 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records