# CVE-2026-90118: ntfs: fix off-by-one page overflow in ntfs_decompress()

> An off-by-one error in the Linux kernel NTFS driver allows out-of-bounds writes when reading corrupted compressed data, potentially leading to code execution or crashes.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-90118, GHSA-fvx8-6m5h-cx99, UBUNTU-CVE-2026-90118

## What is CVE-2026-90118?

CVE-2026-90118 is a high-severity memory corruption vulnerability in Linux, published on 17 Sep 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:

ntfs: fix off-by-one page overflow in ntfs_decompress()

The per-token range check in ntfs_decompress() uses

	if (cb >= cb_sb_end || dp_addr > dp_sb_end)
		break;

so dp_addr == dp_sb_end falls through to the symbol copy
`*dp_addr++ = *cb++`, writing one byte past the destination page.  Since
NTFS_SB_SIZE == PAGE_SIZE the destination is a single page, so the byte
lands in the adjacent page, and *dest_ofs is left one past the sub-block
end (the later `*dest_ofs &= ~PAGE_MASK` then yields 1, not 0, so the page
is never finalized and later sub-blocks keep writing further past it).  A
corrupted compressed $DATA attribute thus produces a bounded run of
out-of-bounds writes when the file is read.

Break as soon as dp_addr reaches dp_sb_end; a full sub-block still
completes, as its final copy advances dp_addr to exactly dp_sb_end.

## Which versions are affected by CVE-2026-90118?


## How do I fix CVE-2026-90118?

Apply the vendor's patch.

## Is CVE-2026-90118 being exploited?

There is no known exploitation of CVE-2026-90118 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90118 and fix it if it is affected.

What it is: CVE-2026-90118 is a high-severity memory corruption vulnerability in Linux, published on 17 Sep 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-2026-90118 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-2026-90118/ (Markdown: https://insights.sbomify.com/CVE-2026-90118/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90118
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90118
- OSV: https://osv.dev/vulnerability/CVE-2026-90118

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90118/
Summaries are generated and may contain mistakes; the official description above is the record.