TI-2021-21673 Aliases CVE-2021-47008 GHSA-9pjj-2jvj-24rm

KVM: SVM: Make sure GHCB is mapped before updating

LOW 24CWE-476Published 2024-02-28 · Updated 2026-05-11

Key facts

Attack vector: Local
Privileges required: Low
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Partial Red Hat: 2 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-476.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00236 14th percentileScored 2026-11-07

Fix Partial Linux (Linux): 5.11.22, 5.12.5, 5.13Red Hat: 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Linux	Linux	5.11 and later	5.11.22, 5.12.5, 5.13	Patch available	CNA

Linux VendorLinux Affected 5.11 and later Fixed in 5.11.22, 5.12.5, 5.13 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:o:linux:linux_kernel::::::::	5.11 to before 5.11.22; 5.12 to before 5.12.5	Vulnerable	Linux

cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 5.11 to before 5.11.22; 5.12 to before 5.12.5 Vulnerable ·Linux

Remediation

Fix · CNA Linux (Linux) Fixed in 5.11.22, 5.12.5, 5.13

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
Red Hat Enterprise Linux 6	Affected	No fix planned: Out of support scope
Red Hat Enterprise Linux 7	Affected	No fix planned: Out of support scope

Not affected: 2 products

Red Hat Enterprise Linux 8
Red Hat Enterprise Linux 9

Timeline

2026-10-02 Threatist record created from CVE-2021-47008
2026-10-03 Alias added: GHSA-9pjj-2jvj-24rm

References

Patch 3

TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3

See all 15278 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences