# CVE-2026-31593: KVM: SEV: Reject attempts to sync VMSA of an already-launched/encrypted vCPU

> A local attacker can crash the host kernel by triggering an RMP violation when syncing VMSA of an already-launched SEV-SNP vCPU.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Apr 2026
- **Updated:** 14 Jun 2026
- **Also known as:** AZL-83648, BELL-CVE-2026-31593, DEBIAN-CVE-2026-31593, GHSA-jp87-j2ph-wv29, ROOT-OS-DEBIAN-11-CVE-2026-31593, ROOT-OS-DEBIAN-12-CVE-2026-31593, ROOT-OS-DEBIAN-13-CVE-2026-31593, UBUNTU-CVE-2026-31593

## What is CVE-2026-31593?

CVE-2026-31593 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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().

## Which versions are affected by CVE-2026-31593?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31593?

Apply the vendor's patch.

## Is CVE-2026-31593 being exploited?

There is no known exploitation of CVE-2026-31593 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-31593 and fix it if it is affected.

What it is: CVE-2026-31593 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-31593 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-31593/ (Markdown: https://insights.sbomify.com/CVE-2026-31593/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31593
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31593
- OSV: https://osv.dev/vulnerability/CVE-2026-31593

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31593/
Summaries are generated and may contain mistakes; the official description above is the record.