# CVE-2026-72354: ntfs: avoid stale runlist element dereference in MFT writeback

> A race condition in the Linux kernel NTFS driver allows use-after-free during MFT writeback, potentially leading to code execution or system crash.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-72354, GHSA-2cmf-w788-qhmg, UBUNTU-CVE-2026-72354

## What is CVE-2026-72354?

CVE-2026-72354 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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

ntfs: avoid stale runlist element dereference in MFT writeback

ntfs_write_mft_block() maps each $MFT record through the $MFT data
runlist. For sub-folio clusters it looks up a struct runlist_element under
ni->runlist.lock, drops the lock, and later uses rl->length and rl->vcn
when choosing folio_sz.

That pointer is only borrowed from ni->runlist.rl. Concurrent $MFT
allocation extension can merge a replacement runlist under the same lock,
and ntfs_rl_realloc() can free the old backing array. If that happens
between the lookup and the later folio_sz decision, writeback can
dereference freed runlist storage.

The buggy scenario involves two paths, with each column showing the order
within that path:

MFT writeback path:               $MFT allocation extension:
1. Look up rl under               1. Extend the $MFT data allocation.
   ni->runlist.lock.              2. Publish a replacement runlist.
2. Drop ni->runlist.lock.         3. Free the old runlist array.
3. Read rl->length and rl->vcn
   to choose folio_sz.

Compute the remaining run length while ni->runlist.lock is still held, and
use that scalar after unlock. This preserves the existing folio sizing
decision without carrying a borrowed runlist_element across the lock
boundary.

Validation reproduced this kernel report:
BUG: KASAN: slab-use-after-free in ntfs_mft_writepages+0x1c8d/0x1fb0

Call Trace:
 <TASK>
 dump_stack_lvl+0x66/0xa0
 print_report+0xce/0x630
 ? ntfs_mft_writepages+0x1c8d/0x1fb0
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? __virt_addr_valid+0x20d/0x410
 ? ntfs_mft_writepages+0x1c8d/0x1fb0
 kasan_report+0xe0/0x110
 ? ntfs_mft_writepages+0x1c8d/0x1fb0
 ntfs_mft_writepages+0x1c8d/0x1fb0
 ? __pfx_ntfs_mft_writepages+0x10/0x10
 ? __pfx___mutex_unlock_slowpath+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? iput+0x92/0xa80
 do_writepages+0x219/0x530
 ? __pfx_do_writepages+0x10/0x10
 __writeback_single_inode+0x117/0xf50
 ? do_raw_spin_lock+0x130/0x270
 ? __pfx_do_raw_spin_lock+0x10/0x10
 ? __pfx___writeback_single_inode+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 writeback_sb_inodes+0x65b/0x1810
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? lock_acquire+0x2b8/0x2f0
 ? __pfx_writeback_sb_inodes+0x10/0x10
 ? lock_release+0x1e0/0x280
 ? _raw_spin_unlock+0x23/0x40
 ? move_expired_inodes+0x2b8/0x850
 __writeback_inodes_wb+0xf4/0x270
 ? __pfx___writeback_inodes_wb+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? queue_io+0x2e4/0x410
 wb_writeback+0x666/0x880
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? __pfx_wb_writeback+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? get_nr_dirty_inodes+0x1c/0x170
 wb_workfn+0x75e/0xbb0
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? _raw_spin_unlock_irqrestore+0x27/0x60
 ? __pfx_wb_workfn+0x10/0x10
 ? __pfx_debug_object_deactivate+0x10/0x10
 ? lock_acquire+0x2b8/0x2f0
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? lock_release+0x1e0/0x280
 process_one_work+0x8d0/0x1870
 ? __pfx_process_one_work+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 worker_thread+0x575/0xf80
 ? __pfx_worker_thread+0x10/0x10
 kthread+0x2e7/0x3c0
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x576/0x810
 ? __pfx_ret_from_fork+0x10/0x10
 ? srso_alias_return_thunk+0x5/0xfbef5
 ? __switch_to+0x57e/0xe10
 ? __switch_to_asm+0x33/0x70
 ? __pfx_kthread+0x10/0x10
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Allocated by task 970:
 kasan_save_stack+0x33/0x60
 kasan_save_track+0x14/0x30
 __kasan_kmalloc+0xaa/0xb0
 __kvmalloc_node_noprof+0x353/0x920
 ntfs_rl_realloc+0x3c/0x80
 ntfs_runlists_merge+0x1212/0x3010
 ntfs_mft_data_extend_allocation_nolock+0x3e0/0x1f40
 ntfs_mft_record_alloc+0x1ab4/0x4f10
 __ntfs_create+0x680/0x2e50
 ntfs_create+0x1e6/0x3a0
 path_openat+0x2b55/0x3c10
 do_file_open+0x1f4/0x460
 do_sys_openat2+0xde/0x170
 __x64_sys_openat+0x122/0x1e0
 do_syscall_64+0x115/0x6a0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 1294:
 kasan_save_
---truncated---

## Which versions are affected by CVE-2026-72354?


## How do I fix CVE-2026-72354?

Apply the vendor's patch.

## Is CVE-2026-72354 being exploited?

There is no known exploitation of CVE-2026-72354 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72354 and fix it if it is affected.

What it is: CVE-2026-72354 is a high-severity use after free vulnerability in Linux, published on 15 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72354 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-2026-72354/ (Markdown: https://insights.sbomify.com/CVE-2026-72354/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72354
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72354
- OSV: https://osv.dev/vulnerability/CVE-2026-72354

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72354/
Summaries are generated and may contain mistakes; the official description above is the record.