# CVE-2026-72193: ntfs3: cap RESTART_TABLE free-chain walker at rt->used

> A crafted NTFS3 disk image causes an infinite loop in the Linux kernel during mount, leading to a system hang or crash.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72193, DEBIAN-CVE-2026-72193, GHSA-33rw-p5m7-q9c2, UBUNTU-CVE-2026-72193

## What is CVE-2026-72193?

CVE-2026-72193 is a denial of service vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

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

ntfs3: cap RESTART_TABLE free-chain walker at rt->used

A crafted NTFS3 disk image triggers an in-kernel infinite loop at
mount time, hanging the mounting thread and firing the soft-lockup
watchdog within ~22s on multi-CPU hosts (panic with
kernel.softlockup_panic=1).  The bug is reachable from desktop USB
auto-mount on distributions where udisks2 routes the NTFS signature
to the in-tree ntfs3 driver (Arch family and an increasing fraction
of Fedora / openSUSE / RHEL deployments); CAP_SYS_ADMIN-class manual
mount elsewhere.

check_rstbl()'s second walker iterates the free-entry singly-linked
list headed by rt->first_free with no upper bound on iteration count:

  for (off = ff; off;) {
      if (off == RESTART_ENTRY_ALLOCATED)
          return false;
      off = le32_to_cpu(*(__le32 *)Add2Ptr(rt, off));
      if (off > ts - sizeof(__le32))
          return false;
  }

The existing guards cover three exits: end-of-list (off == 0), the
in-use marker (off == RESTART_ENTRY_ALLOCATED), and out-of-bounds
(off > ts - sizeof(__le32)).  None of the three prevents an
in-bounds cycle.

A crafted on-disk RESTART_TABLE whose free chain contains a
self-loop or A->B->A cycle whose offsets satisfy:

  - in range [sizeof(struct RESTART_TABLE), ts - sizeof(__le32)]
  - (off - sizeof(struct RESTART_TABLE)) % rsize == 0

passes all existing guards and spins the mount-time thread forever.
Reproduced in UML by hand-forging a 2 MB NTFS3 image whose journal
RESTART_TABLE first_free = 0x18 and whose entry at offset 0x18
stores 0x18 as its next pointer; mount of the forged image with
the in-tree ntfs3 driver never returns.

Bound the walker by rt->used.  Each entry on a legitimate free
chain is unique, and the total slot count is ne = le16_to_cpu
(rt->used).  A traversal that visits more than ne slots is by
construction malformed; reject it as a corrupt RESTART_TABLE.

After this patch, mount of the forged image returns with -EINVAL
and a log_replay failure message, and mkntfs-produced legitimate
images mount cleanly (verified in the same UML harness).

## Which versions are affected by CVE-2026-72193?


## How do I fix CVE-2026-72193?

Apply the vendor's patch.

## Is CVE-2026-72193 being exploited?

There is no known exploitation of CVE-2026-72193 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72193 and fix it if it is affected.

What it is: CVE-2026-72193 is a denial of service vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-72193 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-2026-72193/ (Markdown: https://insights.sbomify.com/CVE-2026-72193/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72193
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72193
- OSV: https://osv.dev/vulnerability/CVE-2026-72193

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72193/
Summaries are generated and may contain mistakes; the official description above is the record.