# CVE-2026-89782: fs/ntfs3: reject restart table growth beyond U16_MAX entries

> An integer overflow in the Linux kernel NTFS3 driver allows out-of-bounds writes when mounting a crafted image, potentially leading to code execution or crashes.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-101427, BELL-CVE-2026-89782, DEBIAN-CVE-2026-89782, GHSA-q8vr-48qg-6qfp, UBUNTU-CVE-2026-89782

## What is CVE-2026-89782?

CVE-2026-89782 is a high-severity vulnerability in Linux, published on 16 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: reject restart table growth beyond U16_MAX entries

During $LogFile replay, log_replay() indexes the transaction table by the
transact_id taken from the log record header.  check_log_rec() only
verifies that transact_id is non-zero and properly aligned, not its
magnitude, so a crafted image can request an arbitrarily large index.

alloc_rsttbl_from_idx() grows the table to cover that index via
extend_rsttbl(), which passes the new entry count to init_rsttbl():

	rt = init_rsttbl(esize, used + add);

used + add is computed as u32 but init_rsttbl() takes a u16, and the
count is stored in struct RESTART_TABLE as a __le16.  When used + add
exceeds U16_MAX it is truncated, init_rsttbl() allocates a table far
smaller than the index requires, and alloc_rsttbl_from_idx() then
dereferences and writes at the original, untruncated offset -- an
out-of-bounds access past the allocation, reachable by mounting a
crafted NTFS image.

 BUG: KASAN: use-after-free in alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950)
 Read of size 4 at addr ffff8880327ffff8 by task exploit
  alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950)
  log_replay (fs/ntfs3/fslog.c:4562)
  ntfs_loadlog_and_replay (fs/ntfs3/fsntfs.c:324)
  ntfs_fill_super (fs/ntfs3/super.c:1393)
  get_tree_bdev_flags
  vfs_get_tree
  path_mount
  __x64_sys_mount

A restart table is limited to U16_MAX entries by its __le16 count, so a
larger growth request is invalid input.  Reject it in extend_rsttbl();
all callers already handle a NULL return.

## Which versions are affected by CVE-2026-89782?


## How do I fix CVE-2026-89782?

Apply the vendor's patch.

## Is CVE-2026-89782 being exploited?

There is no known exploitation of CVE-2026-89782 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89782 and fix it if it is affected.

What it is: CVE-2026-89782 is a high-severity vulnerability in Linux, published on 16 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-2026-89782 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-2026-89782/ (Markdown: https://insights.sbomify.com/CVE-2026-89782/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89782
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89782
- OSV: https://osv.dev/vulnerability/CVE-2026-89782

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89782/
Summaries are generated and may contain mistakes; the official description above is the record.