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high 8.8

CVE-2025-39961 json

iommu/amd/pgtbl: Fix possible race while increase page table level

published last yr. modified 21d ago also EUVD-2025-33337

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 1%
public exploits
0
none known

Summary

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

iommu/amd/pgtbl: Fix possible race while increase page table level

The AMD IOMMU host page table implementation supports dynamic page table levels (up to 6 levels), starting with a 3-level configuration that expands based on IOVA address. The kernel maintains a root pointer and current page table level to enable proper page table walks in alloc_pte()/fetch_pte() operations.

The IOMMU IOVA allocator initially starts with 32-bit address and onces its exhuasted it switches to 64-bit address (max address is determined based on IOMMU and device DMA capability). To support larger IOVA, AMD IOMMU driver increases page table level.

But in unmap path (iommu_v1_unmap_pages()), fetch_pte() reads pgtable->[root/mode] without lock. So its possible that in exteme corner case, when increase_address_space() is updating pgtable->[root/mode], fetch_pte() reads wrong page table level (pgtable->mode). It does compare the value with level encoded in page table and returns NULL. This will result is iommu_unmap ops to fail and upper layer may retry/log WARN_ON.

CPU 0 CPU 1 ------ ------ map pages unmap pages alloc_pte() -> increase_address_space() iommu_v1_unmap_pages() -> fetch_pte() pgtable->root = pte (new root value) READ pgtable->[mode/root] Reads new root, old mode Updates mode (pgtable->mode += 1)

Since Page table level updates are infrequent and already synchronized with a spinlock, implement seqcount to enable lock-free read operations on the read path.

Patch / fix

  • Linux Linux 4.10, 4.15, 4.20, 5.3, 6.6.108, 6.12.49, 6.16.9, 6.17
  • linux Debian 13 6.12.57-1
  • linux Debian 14 6.16.9-1

debian advisories DEBIAN-CVE-2025-39961

  • linux Ubuntu 24.04 LTS 6.8.0-106.106
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1050.53
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1052.55
  • linux-gke Ubuntu 24.04 LTS 6.8.0-1048.53
  • linux-ibm Ubuntu 24.04 LTS 6.8.0-1049.49
  • linux-azure Ubuntu 24.04 LTS 6.8.0-1051.57
  • linux-gkeop Ubuntu 24.04 LTS 6.8.0-1035.38
  • linux-raspi Ubuntu 24.04 LTS 6.8.0-1050.54

ubuntu advisories UBUNTU-CVE-2025-39961

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel-rt Linux Micro 6.2 6.12.0-160000.8.1
  • kernel-64kb SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.8.1
  • kernel-source SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.8.1
  • kernel-default SLES 16.0, SLE High Availability Extension 16.0, Linux Micro 6.2 +1 more 6.12.0-160000.8.1
  • kernel-default-base SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 6.12.0-160000.8.1.160000.2.5
  • kernel-syms SLES 16.0, Linux Micro Extras 6.2, SLES for SAP applications 16.0 6.12.0-160000.8.1
  • kernel-obs-qa SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.8.1
  • kernel-kvmsmall SLES for SAP applications 16.0, SLES 16.0 6.12.0-160000.8.1

suse advisories SUSE-SU-2026:20012-1SUSE-SU-2026:20015-1SUSE-SU-2026:20021-1SUSE-SU-2026:20562-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.8.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.8.1
  • kernel-kvmsmall openSUSE Leap 16.0 6.12.0-160000.8.1

opensuse advisories openSUSE-SU-2025:20172-1

  • kernel Azure Linux 3.0 6.6.112.1-1

azure linux advisories AZL-68348

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-39961 updated cvss 5.3

kernel: iommu/amd/pgtbl: Fix possible race while increase page table level

  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more Red Hat Enterprise Linux 10 kernel
    affected: workaround, no fix available “To mitigate this issue, prevent module amd_iommu from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically.”
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
25d ago

Exploit prediction

0.12% chance of exploitation in the next 30 days, higher than 1% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 4.7 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

  • Linux Linux

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
Technology feeds

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.