# CVE-2026-72185: ntfs: fix WARN_ON for resident attribute in ntfs_map_runlist_nolock()

> A crafted NTFS image triggers a kernel warning and potential instability during mount, causing denial of service.

- **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:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-72185, GHSA-8g34-c4r8-pmf8, UBUNTU-CVE-2026-72185

## What is CVE-2026-72185?

CVE-2026-72185 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: fix WARN_ON for resident attribute in ntfs_map_runlist_nolock()

When ntfs_map_runlist_nolock() needs to look up the attribute extent
containing a target VCN (ctx_needs_reset == true), it calls
ntfs_attr_lookup() and then expects the result to be a non-resident
attribute, since only non-resident attributes have a mapping pairs
array to decompress.

A crafted NTFS image can place a resident attribute where a non-resident
one is expected, causing ntfs_attr_lookup() to succeed but return a
resident attribute record.  Previously this was caught only by a
WARN_ON(), which does not stop execution.  The code then falls through to
read a->data.non_resident.highest_vcn from what is actually a resident
attribute, accessing the wrong union member and corrupting the VCN range
check.

The caller path triggering this warning during mount is:

  ntfs_map_runlist_nolock
  ntfs_empty_logfile
  load_system_files
  ntfs_fill_super

In this path ctx is NULL, so ntfs_map_runlist_nolock() allocates a
temporary search context internally and sets ctx_needs_reset = true.
The existing resident-attribute guard in the ctx != NULL branch already
returns -EIO silently for the same condition; make the ctx_needs_reset
path consistent by replacing the WARN_ON() with the same -EIO error
return.

This causes the crafted image to be rejected with a mount error instead
of triggering a kernel warning.

## Which versions are affected by CVE-2026-72185?


## How do I fix CVE-2026-72185?

Apply the vendor's patch.

## Is CVE-2026-72185 being exploited?

There is no known exploitation of CVE-2026-72185 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72185 and fix it if it is affected.

What it is: CVE-2026-72185 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-2026-72185 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-2026-72185/ (Markdown: https://insights.sbomify.com/CVE-2026-72185/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72185
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72185
- OSV: https://osv.dev/vulnerability/CVE-2026-72185

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72185/
Summaries are generated and may contain mistakes; the official description above is the record.