# CVE-2025-40038: KVM: SVM: Skip fastpath emulation on VM-Exit if next RIP isn't valid

> A guest VM can trigger a kernel crash in the Linux KVM SVM module by causing a sleep in an atomic context during instruction emulation.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Oct 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-40038, DEBIAN-CVE-2025-40038, GHSA-c4m5-3mj6-4mp6, ROOT-OS-DEBIAN-13-CVE-2025-40038, ROOT-OS-UBUNTU-2404-CVE-2025-40038, UBUNTU-CVE-2025-40038

## What is CVE-2025-40038?

CVE-2025-40038 is a high-severity denial of service vulnerability in Linux, published on 28 Oct 2025. 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: SVM: Skip fastpath emulation on VM-Exit if next RIP isn't valid

Skip the WRMSR and HLT fastpaths in SVM's VM-Exit handler if the next RIP
isn't valid, e.g. because KVM is running with nrips=false.  SVM must
decode and emulate to skip the instruction if the CPU doesn't provide the
next RIP, and getting the instruction bytes to decode requires reading
guest memory.  Reading guest memory through the emulator can fault, i.e.
can sleep, which is disallowed since the fastpath handlers run with IRQs
disabled.

 BUG: sleeping function called from invalid context at ./include/linux/uaccess.h:106
 in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 32611, name: qemu
 preempt_count: 1, expected: 0
 INFO: lockdep is turned off.
 irq event stamp: 30580
 hardirqs last  enabled at (30579): [<ffffffffc08b2527>] vcpu_run+0x1787/0x1db0 [kvm]
 hardirqs last disabled at (30580): [<ffffffffb4f62e32>] __schedule+0x1e2/0xed0
 softirqs last  enabled at (30570): [<ffffffffb4247a64>] fpu_swap_kvm_fpstate+0x44/0x210
 softirqs last disabled at (30568): [<ffffffffb4247a64>] fpu_swap_kvm_fpstate+0x44/0x210
 CPU: 298 UID: 0 PID: 32611 Comm: qemu Tainted: G     U              6.16.0-smp--e6c618b51cfe-sleep #782 NONE
 Tainted: [U]=USER
 Hardware name: Google Astoria-Turin/astoria, BIOS 0.20241223.2-0 01/17/2025
 Call Trace:
  <TASK>
  dump_stack_lvl+0x7d/0xb0
  __might_resched+0x271/0x290
  __might_fault+0x28/0x80
  kvm_vcpu_read_guest_page+0x8d/0xc0 [kvm]
  kvm_fetch_guest_virt+0x92/0xc0 [kvm]
  __do_insn_fetch_bytes+0xf3/0x1e0 [kvm]
  x86_decode_insn+0xd1/0x1010 [kvm]
  x86_emulate_instruction+0x105/0x810 [kvm]
  __svm_skip_emulated_instruction+0xc4/0x140 [kvm_amd]
  handle_fastpath_invd+0xc4/0x1a0 [kvm]
  vcpu_run+0x11a1/0x1db0 [kvm]
  kvm_arch_vcpu_ioctl_run+0x5cc/0x730 [kvm]
  kvm_vcpu_ioctl+0x578/0x6a0 [kvm]
  __se_sys_ioctl+0x6d/0xb0
  do_syscall_64+0x8a/0x2c0
  entry_SYSCALL_64_after_hwframe+0x4b/0x53
 RIP: 0033:0x7f479d57a94b
  </TASK>

Note, this is essentially a reapply of commit 5c30e8101e8d ("KVM: SVM:
Skip WRMSR fastpath on VM-Exit if next RIP isn't valid"), but with
different justification (KVM now grabs SRCU when skipping the instruction
for other reasons).

## Which versions are affected by CVE-2025-40038?


## How do I fix CVE-2025-40038?

Apply the vendor's patch.

## Is CVE-2025-40038 being exploited?

There is no known exploitation of CVE-2025-40038 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40038 and fix it if it is affected.

What it is: CVE-2025-40038 is a high-severity denial of service vulnerability in Linux, published on 28 Oct 2025. 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-2025-40038 in the wild and no public exploit code.

Affected product: Linux. 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-2025-40038/ (Markdown: https://insights.sbomify.com/CVE-2025-40038/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40038
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40038
- OSV: https://osv.dev/vulnerability/CVE-2025-40038

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40038/
Summaries are generated and may contain mistakes; the official description above is the record.