# CVE-2026-53108: powerpc/64s: Fix unmap race with PMD migration entries

> A race condition in the Linux kernel's powerpc memory management can cause a kernel bug and system crash during concurrent page migration and unmapping.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/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 Jun 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-90453, BELL-CVE-2026-53108, DEBIAN-CVE-2026-53108, GHSA-2377-3vvp-rhhq, ROOT-OS-DEBIAN-11-CVE-2026-53108, ROOT-OS-DEBIAN-12-CVE-2026-53108, ROOT-OS-DEBIAN-13-CVE-2026-53108, ROOT-OS-UBUNTU-2204-CVE-2026-53108, ROOT-OS-UBUNTU-2404-CVE-2026-53108, UBUNTU-CVE-2026-53108

## What is CVE-2026-53108?

CVE-2026-53108 is a medium-severity vulnerability in Linux kernel, published on 24 Jun 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:

powerpc/64s: Fix unmap race with PMD migration entries

The following race is possible with migration swap entries or
device-private THP entries. e.g. when move_pages is called on a PMD THP
page, then there maybe an intermediate state, where PMD entry acts as
a migration swap entry (pmd_present() is true). Then if an munmap
happens at the same time, then this VM_BUG_ON() can happen in
pmdp_huge_get_and_clear_full().

This patch fixes that.

Thread A: move_pages() syscall
  add_folio_for_migration()
    mmap_read_lock(mm)
    folio_isolate_lru(folio)
    mmap_read_unlock(mm)

  do_move_pages_to_node()
    migrate_pages()
      try_to_migrate_one()
        spin_lock(ptl)
        set_pmd_migration_entry()
          pmdp_invalidate()     # PMD: _PAGE_INVALID | _PAGE_PTE | pfn
          set_pmd_at()          # PMD: migration swap entry (pmd_present=0)
        spin_unlock(ptl)
        [page copy phase]       # <--- RACE WINDOW -->

Thread B: munmap()
  mmap_write_downgrade(mm)
  unmap_vmas() -> zap_pmd_range()
    zap_huge_pmd()
      __pmd_trans_huge_lock()
        pmd_is_huge():          # !pmd_present && !pmd_none -> TRUE (swap entry)
        pmd_lock() -> 		# spin_lock(ptl), waits for Thread A to release ptl
      pmdp_huge_get_and_clear_full()
        VM_BUG_ON(!pmd_present(*pmdp))  # HITS!

[  287.738700][ T1867] ------------[ cut here ]------------
[  287.743843][ T1867] kernel BUG at arch/powerpc/mm/book3s64/pgtable.c:187!
cpu 0x0: Vector: 700 (Program Check) at [c00000044037f4f0]
    pc: c000000000094ca4: pmdp_huge_get_and_clear_full+0x6c/0x23c
    lr: c000000000645dec: zap_huge_pmd+0xb0/0x868
    sp: c00000044037f790
   msr: 800000000282b033
  current = 0xc0000004032c1a00
  paca    = 0xc000000004fe0000   irqmask: 0x03   irq_happened: 0x09
    pid   = 1867, comm = a.out
kernel BUG at :187!
Linux version 6.19.0-12136-g14360d4f917c-dirty (powerpc64le-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40) #27 SMP PREEMPT Sun Feb 22 10:38:56 IST 2026
enter ? for help
[link register   ] c000000000645dec zap_huge_pmd+0xb0/0x868
[c00000044037f790] c00000044037f7d0 (unreliable)
[c00000044037f7d0] c000000000645dcc zap_huge_pmd+0x90/0x868
[c00000044037f840] c0000000005724cc unmap_page_range+0x176c/0x1f40
[c00000044037fa00] c000000000572ea0 unmap_vmas+0xb0/0x1d8
[c00000044037fa90] c0000000005af254 unmap_region+0xb4/0x128
[c00000044037fb50] c0000000005af400 vms_complete_munmap_vmas+0x138/0x310
[c00000044037fbe0] c0000000005b0f1c do_vmi_align_munmap+0x1ec/0x238
[c00000044037fd30] c0000000005b3688 __vm_munmap+0x170/0x1f8
[c00000044037fdf0] c000000000587f74 sys_munmap+0x2c/0x40
[c00000044037fe10] c000000000032668 system_call_exception+0x128/0x350
[c00000044037fe50] c00000000000d05c system_call_vectored_common+0x15c/0x2ec
---- Exception: 3000 (System Call Vectored) at 0000000010064a2c
SP (7fff9b1ee9c0) is in userspace
0:mon> zh

commit a30b48bf1b24 ("mm/migrate_device: implement THP migration of zone device pages"),
enabled migration for device-private PMD entries. Hence this is one
other path where this warning could get trigger from.

 ------------[ cut here ]------------
 WARNING: arch/powerpc/mm/book3s64/hash_pgtable.c:199 at hash__pmd_hugepage_update+0x48/0x284, CPU#3: hmm-tests/1905
 Modules linked in: test_hmm
 CPU: 3 UID: 0 PID: 1905 Comm: hmm-tests Tainted: G    B   W    L   N  7.0.0-rc1-01438-g7e2f0ee7581c #21 PREEMPT
 Tainted: [B]=BAD_PAGE, [W]=WARN, [L]=SOFTLOCKUP, [N]=TEST
 Hardware name: IBM pSeries (emulated by qemu) POWER10 (architected) 0x801200 0xf000006 of:SLOF,git-ee03ae pSeries
 NIP [c000000000096b70] hash__pmd_hugepage_update+0x48/0x284
 LR [c000000000096e7c] hash__pmdp_huge_get_and_clear+0xd0/0xd4
 Call Trace:
 [c000000604707670] [c000000004e102b8] 0xc000000004e102b8 (unreliable)
 [c000000604707700] [c00000000064ec3c] set_pmd_migration_entry+0x414/0x498
 [c000000604707760] [c00000000063e5a4] migrate_vma_col
---truncated---

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-53108?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53108?

Apply the vendor's patch.

## Is CVE-2026-53108 being exploited?

There is no known exploitation of CVE-2026-53108 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-2026-53108 and fix it if it is affected.

What it is: CVE-2026-53108 is a medium-severity vulnerability in Linux kernel, published on 24 Jun 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-2026-53108 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-2026-53108/ (Markdown: https://insights.sbomify.com/CVE-2026-53108/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53108
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53108
- OSV: https://osv.dev/vulnerability/CVE-2026-53108

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53108/
Summaries are generated and may contain mistakes; the official description above is the record.