# CVE-2026-72195: fs/ntfs3: bound attr_off in UpdateResidentValue against data_off

> An integer underflow in the Linux kernel NTFS3 driver allows out-of-bounds reads, potentially causing system crashes or leaking memory contents.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/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:** 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-2026-72195, DEBIAN-CVE-2026-72195, GHSA-44j2-h353-38w7, UBUNTU-CVE-2026-72195

## What is CVE-2026-72195?

CVE-2026-72195 is a high-severity 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: bound attr_off in UpdateResidentValue against data_off

In do_action()'s UpdateResidentValue case (fslog.c:3307),
lrh->attr_off and lrh->redo_len come from the on-disk LRH.
When they satisfy aoff + dlen < attr->res.data_off, the
assignment

	attr->res.data_size = cpu_to_le32(aoff + dlen - data_off);

underflows to ~4 GiB (e.g. 0xFFFFFFF9 when aoff=0x10, dlen=1,
data_off=0x18).  Subsequent code that reads attr->res.data_size
to walk the resident attribute payload would then read up to
4 GiB past the 1024-byte MFT record allocation.

The existing mi_enum_attr() defense in fs/ntfs3/record.c:287
catches the corrupted data_size on the next attribute walk
and fails the mount, but only on the path that walks all
attributes.  A read site that picks an attribute by name and
reads its data_size without re-validating is not covered.
Validate aoff against data_off and asize at the source.

Reproduced under UML+KASAN on mainline 8d90b09e6741 via
pr_warn-only probe: with aoff=0x10 and data_off=0x18, the
post-assignment data_size is 0xfffffff9 (mount then fails
at -22 from mi_enum_attr).

[almaz.alexandrovich@paragon-software.com: clang-formatted the changes]

## Which versions are affected by CVE-2026-72195?


## How do I fix CVE-2026-72195?

Apply the vendor's patch.

## Is CVE-2026-72195 being exploited?

There is no known exploitation of CVE-2026-72195 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72195 and fix it if it is affected.

What it is: CVE-2026-72195 is a high-severity 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-2026-72195 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-2026-72195/ (Markdown: https://insights.sbomify.com/CVE-2026-72195/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72195
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72195
- OSV: https://osv.dev/vulnerability/CVE-2026-72195

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72195/
Summaries are generated and may contain mistakes; the official description above is the record.