# CVE-2026-72478: fs/ntfs3: add bounds check to run_get_highest_vcn()

> A missing bounds check in the Linux kernel NTFS3 driver allows out-of-bounds reads during mount, potentially causing crashes or leaking memory.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72478, DEBIAN-CVE-2026-72478, GHSA-pcrg-m6wx-53ch, UBUNTU-CVE-2026-72478

## What is CVE-2026-72478?

CVE-2026-72478 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 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:

fs/ntfs3: add bounds check to run_get_highest_vcn()

run_get_highest_vcn() parses a packed NTFS mapping-pairs buffer without
any length bound, relying solely on a 0x00 terminator to stop.  A
crafted $LogFile UpdateMappingPairs record whose embedded attribute
contains mapping-pairs runs without a terminator causes the function to
read past the slab allocation, triggering a KASAN slab-out-of-bounds
read on mount.

The sibling function run_unpack() received an analogous bounds-check in
commit b62567bca474 ("ntfs3: add buffer boundary checks to run_unpack()"),
but run_get_highest_vcn() was missed.

Take a run_buf_size parameter and reject any run header whose payload
would extend past the buffer end, mirroring the pattern used by
run_unpack().  The caller in fslog.c passes the remaining attribute
bytes after the mapping-pairs offset.

KASAN report (on mainline v7.1 merge window HEAD):

  BUG: KASAN: slab-out-of-bounds in run_get_highest_vcn+0x3c0/0x410
  Read of size 1 at addr ffff88800e2d5400 by task mount/72
  Call Trace:
   run_get_highest_vcn+0x3c0/0x410
   do_action.isra.0+0x3ba8/0x7b50
   log_replay+0x9ddd/0x10200
   ntfs_loadlog_and_replay+0x4ad/0x610
   ntfs_fill_super+0x214a/0x4540

## Which versions are affected by CVE-2026-72478?


## How do I fix CVE-2026-72478?

Apply the vendor's patch.

## Is CVE-2026-72478 being exploited?

There is no known exploitation of CVE-2026-72478 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72478 and fix it if it is affected.

What it is: CVE-2026-72478 is a high-severity memory corruption vulnerability in Linux, published on 15 Aug 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-2026-72478 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-2026-72478/ (Markdown: https://insights.sbomify.com/CVE-2026-72478/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72478
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72478
- OSV: https://osv.dev/vulnerability/CVE-2026-72478

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72478/
Summaries are generated and may contain mistakes; the official description above is the record.