# CVE-2026-72211: ntfs: grow index root value before reparent header update

> A logic error in the Linux kernel NTFS driver can cause filesystem corruption and denial of service during index root reparenting operations.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-72211, GHSA-mw2v-m8cx-mx72, UBUNTU-CVE-2026-72211

## What is CVE-2026-72211?

CVE-2026-72211 is a critical denial of service vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

ntfs: grow index root value before reparent header update

ntfs_ir_reparent() moves the resident index root entries into an index
block and leaves a small root stub containing the child VCN. That root
stub can be larger than the existing resident value. For example, an
empty root with value_length 48 has an index area of 32 bytes, while the
large-index root stub needs index_length and allocated_size of 40 bytes.

The current code publishes the larger index.index_length and
index.allocated_size before resizing the resident value. If the resize
returns -ENOSPC, the recovery path can call ntfs_inode_add_attrlist(),
which looks attributes up again while the root header says
allocated_size 40 but the resident value still only provides 32 bytes of
index area. Lookup-time $INDEX_ROOT validation then correctly rejects
that transient layout as corrupt.

This reproduces as a generic/013 failure under qemu. In the failing run,
the transient root had value_len=48, index_size=32, index_length=40, and
allocated_size=40, and ntfsprogs-plus ntfsck reported "Corrupt index
root in MFT record 1177".

When the root stub grows, resize the resident value before publishing the
larger root header. If the resize fails, the old root remains valid for
recovery lookups. Keep the existing header-before-resize ordering for
shrink or same-size cases so the resident value never temporarily
exposes an allocated_size beyond its bounds.

## Which versions are affected by CVE-2026-72211?


## How do I fix CVE-2026-72211?

Apply the vendor's patch.

## Is CVE-2026-72211 being exploited?

There is no known exploitation of CVE-2026-72211 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72211 and fix it if it is affected.

What it is: CVE-2026-72211 is a critical denial of service vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72211 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-2026-72211/ (Markdown: https://insights.sbomify.com/CVE-2026-72211/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72211
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72211
- OSV: https://osv.dev/vulnerability/CVE-2026-72211

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72211/
Summaries are generated and may contain mistakes; the official description above is the record.