# CVE-2026-97439: fs/ntfs3: preserve non-DOS attribute bits in system.dos_attrib

> A local attacker can cause a kernel crash via a NULL pointer dereference in the ntfs3 filesystem driver by manipulating file attributes.

- **Severity:** Not scored
- **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 Sep 2026
- **Updated:** 3 Oct 2026
- **Also known as:** AZL-103625, BELL-CVE-2026-97439, DEBIAN-CVE-2026-97439, GHSA-rc9g-r7vc-2qq2, UBUNTU-CVE-2026-97439

## What is CVE-2026-97439?

CVE-2026-97439 is a vulnerability in Linux, published on 24 Sep 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: preserve non-DOS attribute bits in system.dos_attrib

[BUG]
A corrupted ntfs3 image can hit a NULL function pointer call in
generic_perform_write() after toggling system.ntfs_attrib and then
overwriting system.dos_attrib on the same file.

BUG: kernel NULL pointer dereference, address: 0000000000000000
\#PF: supervisor instruction fetch in kernel mode
\#PF: error_code(0x0010) - not-present page
PGD bed5067 P4D bed5067 PUD 0
Oops: Oops: 0010 [#1] SMP KASAN NOPTI
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffff88801025f988 EFLAGS: 00010246
Call Trace:
 generic_perform_write+0x409/0x8c0 mm/filemap.c:4255
 __generic_file_write_iter+0x1bb/0x200 mm/filemap.c:4372
 ntfs_file_write_iter+0xcd9/0x1c20 fs/ntfs3/file.c:1253
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x63b/0xf70 fs/read_write.c:686
 ksys_write+0x133/0x250 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x77/0xc0 fs/read_write.c:746
 ...

[CAUSE]
system.ntfs_attrib updates ATTR_DATA flags via ni_new_attr_flags()
and switches i_mapping->a_ops to ntfs_aops_cmpr when
FILE_ATTRIBUTE_COMPRESSED is set. system.dos_attrib then overwrites
ni->std_fa from a one-byte DOS attribute value, clearing the compression
bit without updating ATTR_DATA or the mapping operations.

Old buffered writes use is_compressed(ni) to choose
__generic_file_write_iter(). That leaves generic_perform_write() calling
a NULL write_begin callback from ntfs_aops_cmpr.

[FIX]
Treat system.dos_attrib as a low-byte DOS attribute update and preserve the
existing non-DOS attribute bits in ni->std_fa. This keeps compressed and
sparse state consistent with ATTR_DATA and the mapping operations while
keeping the existing DOS attribute semantics intact.

## Which versions are affected by CVE-2026-97439?


## How do I fix CVE-2026-97439?

Apply the vendor's patch.

## Is CVE-2026-97439 being exploited?

There is no known exploitation of CVE-2026-97439 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97439 and fix it if it is affected.

What it is: CVE-2026-97439 is a vulnerability in Linux, published on 24 Sep 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-2026-97439 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-2026-97439/ (Markdown: https://insights.sbomify.com/CVE-2026-97439/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97439
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97439
- OSV: https://osv.dev/vulnerability/CVE-2026-97439

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97439/
Summaries are generated and may contain mistakes; the official description above is the record.