CVE-2025-68810: KVM: Disallow toggling KVM_MEM_GUEST_MEMFD on an existing memslot

Published Jan 13, 2026
·
Updated

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

KVM: Disallow toggling KVMMEMGUESTMEMFD on an existing memslot

Reject attempts to disable KVMMEMGUESTMEMFD on a memslot that was initially created with a guestmemfd binding, as KVM doesn't support toggling KVMMEMGUESTMEMFD on existing memslots. KVM prevents enabling KVMMEMGUESTMEMFD, but doesn't prevent clearing the flag.

Failure to reject the new memslot results in a use-after-free due to KVM not unbinding from the guestmemfd instance. Unbinding on a FLAGSONLY change is easy enough, and can/will be done as a hardening measure (in anticipation of KVM supporting dirty logging on guestmemfd at some point), but fixing the use-after-free would only address the immediate symptom.

================================================================== BUG: KASAN: slab-use-after-free in kvmgmemrelease+0x362/0x400 [kvm] Write of size 8 at addr ffff8881111ae908 by task repro/745

CPU: 7 UID: 1000 PID: 745 Comm: repro Not tainted 6.18.0-rc6-115d5de2eef3-next-kasan #3 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 Call Trace: <TASK> dumpstacklvl+0x51/0x60 printreport+0xcb/0x5c0 kasanreport+0xb4/0xe0 kvmgmemrelease+0x362/0x400 [kvm] fput+0x2fa/0x9d0 taskworkrun+0x12c/0x200 doexit+0x6ae/0x2100 dogroupexit+0xa8/0x230 x64sysexitgroup+0x3a/0x50 x64syscall+0x737/0x740 dosyscall64+0x5b/0x900 entrySYSCALL64afterhwframe+0x4b/0x53 RIP: 0033:0x7f581f2eac31 </TASK>

Allocated by task 745 on cpu 6 at 9.746971s: kasansavestack+0x20/0x40 kasansavetrack+0x13/0x50 kasankmalloc+0x77/0x90 kvmsetmemoryregion.part.0+0x652/0x1110 [kvm] kvmvmioctl+0x14b0/0x3290 [kvm] x64sysioctl+0x129/0x1a0 dosyscall64+0x5b/0x900 entrySYSCALL64afterhwframe+0x4b/0x53

Freed by task 745 on cpu 6 at 9.747467s: kasansavestack+0x20/0x40 kasansavetrack+0x13/0x50 kasansavefreeinfo+0x37/0x50 kasanslabfree+0x3b/0x60 kfree+0xf5/0x440 kvmsetmemslot+0x3c2/0x1160 [kvm] kvmsetmemoryregion.part.0+0x86a/0x1110 [kvm] kvmvmioctl+0x14b0/0x3290 [kvm] x64sysioctl+0x129/0x1a0 dosyscall64+0x5b/0x900 entrySYSCALL64afterhwframe+0x4b/0x53

Affected Software

2 affected componentsFixes available
linux-kernel<=6.18.0-rc6-115d5de2eef3-next-kasan
debian/linux
6.1.176-16.1.190-16.12.107-16.12.115-27.2.12-17.2.15-1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade debian/linux to a version that resolves this vulnerability.

    Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1
  2. Upgrade

    Upgrade ubuntu/linux-aws-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1052.55~22.04.1
  3. Upgrade

    Upgrade ubuntu/linux-azure-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1059.65~22.04.1
  4. Upgrade

    Upgrade ubuntu/linux-azure-fde-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1058.65~22.04.1
  5. Upgrade

    Upgrade ubuntu/linux-gcp-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1054.57~22.04.1
  6. Upgrade

    Upgrade ubuntu/linux-hwe-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-110.110~22.04.1
  7. Upgrade

    Upgrade ubuntu/linux-ibm-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1051.51~22.04.1
  8. Upgrade

    Upgrade ubuntu/linux-lowlatency-hwe-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-110.110.1~22.04.1
  9. Upgrade

    Upgrade ubuntu/linux-nvidia-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1051.54~22.04.1
  10. Upgrade

    Upgrade ubuntu/linux-oracle-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-1049.50~22.04.1
  11. Upgrade

    Upgrade ubuntu/linux-riscv-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.0-110.110~22.04.1
  12. Upgrade

    Upgrade ubuntu/linux-realtime-6.8 to a version that resolves this vulnerability.

    Fixed in 6.8.1-1047.48~22.04.1
  13. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 6.8.0-110.110
  14. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 6.8.0-1052.55
  15. Upgrade

    Upgrade ubuntu/linux-aws-6.17 to a version that resolves this vulnerability.

    Fixed in 6.17.0-1012.12~24.04.1
  16. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 6.8.0-1054.60
  17. Upgrade

    Upgrade ubuntu/linux-azure-6.17 to a version that resolves this vulnerability.

    Fixed in 6.17.0-1013.13~24.04.1
  18. Upgrade

    Upgrade ubuntu/linux-azure-fde to a version that resolves this vulnerability.

    Fixed in 6.8.0-1058.65
  19. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 6.8.0-1054.57
  20. Upgrade

    Upgrade ubuntu/linux-gcp-6.17 to a version that resolves this vulnerability.

    Fixed in 6.17.0-1012.12~24.04.1
  21. Upgrade

    Upgrade ubuntu/linux-gke to a version that resolves this vulnerability.

    Fixed in 6.8.0-1050.56
  22. Upgrade

    Upgrade ubuntu/linux-gkeop to a version that resolves this vulnerability.

    Fixed in 6.8.0-1037.40
  23. Upgrade

    Upgrade ubuntu/linux-hwe-6.17 to a version that resolves this vulnerability.

    Fixed in 6.17.0-22.22~24.04.1
  24. Upgrade

    Upgrade ubuntu/linux-ibm to a version that resolves this vulnerability.

    Fixed in 6.8.0-1051.51
  25. Upgrade

    Upgrade ubuntu/linux-lowlatency to a version that resolves this vulnerability.

    Fixed in 6.8.0-110.110.1
  26. Upgrade

    Upgrade ubuntu/linux-nvidia to a version that resolves this vulnerability.

    Fixed in 6.8.0-1051.54
  27. Upgrade

    Upgrade ubuntu/linux-nvidia-6.17 to a version that resolves this vulnerability.

    Fixed in 6.17.0-1018.18
  28. Upgrade

    Upgrade ubuntu/linux-nvidia-lowlatency to a version that resolves this vulnerability.

    Fixed in 6.8.0-1051.54.1
  29. Upgrade

    Upgrade ubuntu/linux-nvidia-tegra to a version that resolves this vulnerability.

    Fixed in 6.8.0-1022.22
  30. Upgrade

    Upgrade ubuntu/linux-oem-6.17 to a version that resolves this vulnerability.

    Fixed in 6.17.0-1020.20
  31. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 6.8.0-1049.50
  32. Upgrade

    Upgrade ubuntu/linux-oracle-6.17 to a version that resolves this vulnerability.

    Fixed in 6.17.0-1011.11~24.04.1
  33. Upgrade

    Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.

    Fixed in 6.8.0-1052.56
  34. Upgrade

    Upgrade ubuntu/linux-riscv-6.17 to a version that resolves this vulnerability.

    Fixed in 6.17.0-22.22.1~24.04.1
  35. Upgrade

    Upgrade ubuntu/linux-xilinx to a version that resolves this vulnerability.

    Fixed in 6.8.0-1028.29
  36. Upgrade

    Upgrade ubuntu/linux-bluefield to a version that resolves this vulnerability.

    Fixed in 6.8.0-1017.21
  37. Upgrade

    Upgrade ubuntu/linux-raspi-realtime to a version that resolves this vulnerability.

    Fixed in 6.8.0-2042.43
  38. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 6.8.1-1047.48
  39. Upgrade

    Upgrade ubuntu/linux-realtime-6.17 to a version that resolves this vulnerability.

    Fixed in 6.17.0-1010.11~24.04.1
  40. Upgrade

    Upgrade ubuntu/linux-aws-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1052.55+fips1
  41. Upgrade

    Upgrade ubuntu/linux-azure-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1053.59+fips1
  42. Upgrade

    Upgrade ubuntu/linux-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-110.110+fips2
  43. Upgrade

    Upgrade ubuntu/linux-gcp-fips to a version that resolves this vulnerability.

    Fixed in 6.8.0-1054.57+fips1
  44. Upgrade

    Upgrade ubuntu/linux to a version that resolves this vulnerability.

    Fixed in 6.17.0-22.22
  45. Upgrade

    Upgrade ubuntu/linux-aws to a version that resolves this vulnerability.

    Fixed in 6.17.0-1012.12
  46. Upgrade

    Upgrade ubuntu/linux-azure to a version that resolves this vulnerability.

    Fixed in 6.17.0-1013.13
  47. Upgrade

    Upgrade ubuntu/linux-gcp to a version that resolves this vulnerability.

    Fixed in 6.17.0-1012.12
  48. Upgrade

    Upgrade ubuntu/linux-oracle to a version that resolves this vulnerability.

    Fixed in 6.17.0-1011.11
  49. Upgrade

    Upgrade ubuntu/linux-raspi to a version that resolves this vulnerability.

    Fixed in 6.17.0-1013.13
  50. Upgrade

    Upgrade ubuntu/linux-realtime to a version that resolves this vulnerability.

    Fixed in 6.17.0-1010.11
  51. Upgrade

    Upgrade ubuntu/linux-riscv to a version that resolves this vulnerability.

    Fixed in 6.17.0-22.22.1

Event History

Jan 13, 2026
CVE Published
via MITRE·03:29 PM
Data Sourced
via MITRE·03:29 PM
DescriptionSeverity
Data Sourced
via NVD·04:16 PM
DescriptionSeverity

Parent advisories

This vulnerability appears in the following advisories.

Frequently Asked Questions

1

What is the severity of CVE-2025-68810?

CVE-2025-68810 has a medium severity rating as it impacts KVM functionality in the Linux kernel.

2

How do I fix CVE-2025-68810?

To fix CVE-2025-68810, ensure you update your Linux kernel to a version that is higher than 6.18.0-rc6-115d5de2eef3-next-kasan.

3

What systems are affected by CVE-2025-68810?

CVE-2025-68810 affects the Linux kernel versions up to 6.18.0-rc6-115d5de2eef3-next-kasan when using KVM.

4

What is the impact of CVE-2025-68810?

CVE-2025-68810 prevents disabling KVM_MEM_GUEST_MEMFD on existing memory slots, which could affect virtual machine performance and security.

5

How was CVE-2025-68810 discovered?

CVE-2025-68810 was identified during routine code reviews and security assessments of the KVM module in the Linux kernel.

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