dbcve.org
Linux KernelOperating system · Linux

CVE-2025-37922

MEDIUM · 5.5 CVSS v3.1 Published 2025-05-20
Fix available
A fix is available. Upgrade to 6.6.90 / 6.12.28 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: book3s64/radix : Align section vmemmap start address to PAGE_SIZE A vmemmap altmap is a device-provided region used to provide backing storage for struct pages. For each namespace, the altmap should belong to that same namespace. If the namespaces are created unaligned, there is a chance that the section vmemmap start address could also be unaligned. If the section vmemmap start address is unaligned, the altmap page allocated from the current namespace might be used by the previous namespace also. During the free operation, since the altmap is shared between two namespaces, the previous namespace may detect that the page does not belong to its altmap and incorrectly assume that the page is a normal page. It then attempts to free the normal page, which leads to a kernel crash. Kernel attempted to read user page (18) - exploit attempt? (uid: 0) BUG: Kernel NULL pointer dereference on read at 0x00000018 Faulting instruction address: 0xc000000000530c7c Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries CPU: 32 PID: 2104 Comm: ndctl Kdump: loaded Tainted: G W NIP: c000000000530c7c LR: c000000000530e00 CTR: 0000000000007ffe REGS: c000000015e57040 TRAP: 0300 Tainted: G W MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 84482404 CFAR: c000000000530dfc DAR: 0000000000000018 DSISR: 40000000 IRQMASK: 0 GPR00: c000000000530e00 c000000015e572e0 c000000002c5cb00 c00c000101008040 GPR04: 0000000000000000 0000000000000007 0000000000000001 000000000000001f GPR08: 0000000000000005 0000000000000000 0000000000000018 0000000000002000 GPR12: c0000000001d2fb0 c0000060de6b0080 0000000000000000 c0000060dbf90020 GPR16: c00c000101008000 0000000000000001 0000000000000000 c000000125b20f00 GPR20: 0000000000000001 0000000000000000 ffffffffffffffff c00c000101007fff GPR24: 0000000000000001 0000000000000000 0000000000000000 0000000000000000 GPR28: 0000000004040201 0000000000000001 0000000000000000 c00c000101008040 NIP [c000000000530c7c] get_pfnblock_flags_mask+0x7c/0xd0 LR [c000000000530e00] free_unref_page_prepare+0x130/0x4f0 Call Trace: free_unref_page+0x50/0x1e0 free_reserved_page+0x40/0x68 free_vmemmap_pages+0x98/0xe0 remove_pte_table+0x164/0x1e8 remove_pmd_table+0x204/0x2c8 remove_pud_table+0x1c4/0x288 remove_pagetable+0x1c8/0x310 vmemmap_free+0x24/0x50 section_deactivate+0x28c/0x2a0 __remove_pages+0x84/0x110 arch_remove_memory+0x38/0x60 memunmap_pages+0x18c/0x3d0 devm_action_release+0x30/0x50 release_nodes+0x68/0x140 devres_release_group+0x100/0x190 dax_pmem_compat_release+0x44/0x80 [dax_pmem_compat] device_for_each_child+0x8c/0x100 [dax_pmem_compat_remove+0x2c/0x50 [dax_pmem_compat] nvdimm_bus_remove+0x78/0x140 [libnvdimm] device_remove+0x70/0xd0 Another issue is that if there is no altmap, a PMD-sized vmemmap page will be allocated from RAM, regardless of the alignment of the section start address. If the section start address is not aligned to the PMD size, a VM_BUG_ON will be triggered when setting the PMD-sized page to page table. In this patch, we are aligning the section vmemmap start address to PAGE_SIZE. After alignment, the start address will not be part of the current namespace, and a normal page will be allocated for the vmemmap mapping of the current section. For the remaining sections, altmaps will be allocated. During the free operation, the normal page will be correctly freed. In the same way, a PMD_SIZE vmemmap page will be allocated only if the section start address is PMD_SIZE-aligned; otherwise, it will fall back to a PAGE-sized vmemmap allocation. Without this patch ================== NS1 start NS2 start _________________________________________________________ | NS1 | NS2 | --------------------------------------------------------- | Altmap| Altmap | .....|Altmap| Altmap | ........... | NS1 | NS1 ---truncated---

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-476

The code follows a pointer that is null, crashing the process. An attacker who can reliably trigger it turns the crash into a denial of service. The fix is checking for null before use and handling the failure path gracefully.

General guidance for the null pointer dereference class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 6.6, < 6.6.90>= 6.7, < 6.12.28>= 6.13, < 6.14.6= 6.15

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.6.90 / 6.12.28 / 6.14.6 or later
Fixed in 6.6.906.12.286.14.6
Vendor patch git.kernel.org →
Recommended fix High confidence

6.6.90 (for 6.6.x users), 6.12.28 (for 6.7-6.12.x users), or 6.14.6 (for 6.13-6.14.x users). For 6.15 users, wait for 6.15.1 or apply the upstream patch.

  1. Upgrade the Linux kernel to one of the fixed releases: 6.6.90, 6.12.28, 6.14.6, or a later version in your respective stable branch.
  2. For distribution kernels, apply the vendor-provided security update containing the fix commit 400be767deaf31a073c6d14c5d151ae5ac2a60e2.
  3. Reboot the system into the new kernel to apply the fix.
  4. After reboot, verify the running kernel version matches the fixed release using 'uname -r'.
Caveat Kernel upgrades may require rebuilding out-of-tree modules; ensure driver compatibility before upgrading production systems.

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $2,850. Get the upgrade done

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-37922 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-37922 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data