---
id: CVE-2026-31593
title: 'KVM: SEV: Reject attempts to sync VMSA of an already-launched/encrypted vCPU'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  KVM: SEV: Reject attempts to sync VMSA of an already-launched/encrypted vCPU

  Reject synchronizing vCPU state to its associated VMSA if the vCPU has
  already been launch…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= ad27ce155566f2b4400fa865859834592bd18777 <
    c9609847ae65ca36233077c2b6cb2bc0fb37c77a
  - >-
    Linux >= ad27ce155566f2b4400fa865859834592bd18777 <
    692fdf05e55fa03960a1278afdc2478c12daea13
  - >-
    Linux >= ad27ce155566f2b4400fa865859834592bd18777 <
    6ef109e01e1d35199e1a97ea68bdfd3cf3fbf9ab
  - >-
    Linux >= ad27ce155566f2b4400fa865859834592bd18777 <
    8f85a4885eee8cb495961ffa371a91828afb9445
  - >-
    Linux >= ad27ce155566f2b4400fa865859834592bd18777 <
    9b9f7962e3e879d12da2bf47e02a24ec51690e3d
  - Linux 6.11
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T15:22:29.586532Z'
published: '2026-04-24'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T15:32:19.282Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31593'
references:
  - url: 'https://git.kernel.org/stable/c/c9609847ae65ca36233077c2b6cb2bc0fb37c77a'
  - url: 'https://git.kernel.org/stable/c/692fdf05e55fa03960a1278afdc2478c12daea13'
  - url: 'https://git.kernel.org/stable/c/6ef109e01e1d35199e1a97ea68bdfd3cf3fbf9ab'
  - url: 'https://git.kernel.org/stable/c/8f85a4885eee8cb495961ffa371a91828afb9445'
  - url: 'https://git.kernel.org/stable/c/9b9f7962e3e879d12da2bf47e02a24ec51690e3d'
tags:
  - cve.org
epss: 0.00122
epssPercentile: 0.01982
ingestedAt: '2026-11-06T15:54:04.057Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

KVM: SEV: Reject attempts to sync VMSA of an already-launched/encrypted vCPU

Reject synchronizing vCPU state to its associated VMSA if the vCPU has
already been launched, i.e. if the VMSA has already been encrypted.  On a
host with SNP enabled, accessing guest-private memory generates an RMP #PF
and panics the host.

  BUG: unable to handle page fault for address: ff1276cbfdf36000
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x80000003) - RMP violation
  PGD 5a31801067 P4D 5a31802067 PUD 40ccfb5063 PMD 40e5954063 PTE 80000040fdf36163
  SEV-SNP: PFN 0x40fdf36, RMP entry: [0x6010fffffffff001 - 0x000000000000001f]
  Oops: Oops: 0003 [#1] SMP NOPTI
  CPU: 33 UID: 0 PID: 996180 Comm: qemu-system-x86 Tainted: G           OE
  Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
  Hardware name: Dell Inc. PowerEdge R7625/0H1TJT, BIOS 1.5.8 07/21/2023
  RIP: 0010:sev_es_sync_vmsa+0x54/0x4c0 [kvm_amd]
  Call Trace:
   <TASK>
   snp_launch_update_vmsa+0x19d/0x290 [kvm_amd]
   snp_launch_finish+0xb6/0x380 [kvm_amd]
   sev_mem_enc_ioctl+0x14e/0x720 [kvm_amd]
   kvm_arch_vm_ioctl+0x837/0xcf0 [kvm]
   kvm_vm_ioctl+0x3fd/0xcc0 [kvm]
   __x64_sys_ioctl+0xa3/0x100
   x64_sys_call+0xfe0/0x2350
   do_syscall_64+0x81/0x10f0
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
  RIP: 0033:0x7ffff673287d
   </TASK>

Note, the KVM flaw has been present since commit ad73109ae7ec ("KVM: SVM:
Provide support to launch and run an SEV-ES guest"), but has only been
actively dangerous for the host since SNP support was added.  With SEV-ES,
KVM would "just" clobber guest state, which is totally fine from a host
kernel perspective since userspace can clobber guest state any time before
sev_launch_update_vmsa().

## Affected

- `Linux >= ad27ce155566f2b4400fa865859834592bd18777 < c9609847ae65ca36233077c2b6cb2bc0fb37c77a`
- `Linux >= ad27ce155566f2b4400fa865859834592bd18777 < 692fdf05e55fa03960a1278afdc2478c12daea13`
- `Linux >= ad27ce155566f2b4400fa865859834592bd18777 < 6ef109e01e1d35199e1a97ea68bdfd3cf3fbf9ab`
- `Linux >= ad27ce155566f2b4400fa865859834592bd18777 < 8f85a4885eee8cb495961ffa371a91828afb9445`
- `Linux >= ad27ce155566f2b4400fa865859834592bd18777 < 9b9f7962e3e879d12da2bf47e02a24ec51690e3d`
- `Linux 6.11`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.