# CVE-2026-90161: erofs: fix interlaced ztailpacking pclusters

> A crafted EROFS filesystem image can trigger an out-of-bounds read, leaking kernel memory to userspace via the page cache.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/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:** 21 Oct 2026
- **Also known as:** AZL-103047, BELL-CVE-2026-90161, DEBIAN-CVE-2026-90161, GHSA-75m6-v57w-mhq4, UBUNTU-CVE-2026-90161

## What is CVE-2026-90161?

CVE-2026-90161 is a high-severity 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:

erofs: fix interlaced ztailpacking pclusters

On-disk sizes of interlaced pclusters should be block-aligned, and
ztailpacking interlaced pclusters should be invalid at all.

Currently, mkfs.erofs won't generate any interlaced pcluster with
ztailpacking enabled, so this doesn't affect any existing valid
filesystems.

However, crafted images can contain invalid interlaced ztailpacking
pclusters, resulting in an out-of-bounds read from a kmap'd page and
copying irrelevant kernel memory into userspace-visible page cache.

## Which versions are affected by CVE-2026-90161?


## How do I fix CVE-2026-90161?

Apply the vendor's patch.

## Is CVE-2026-90161 being exploited?

There is no known exploitation of CVE-2026-90161 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90161 and fix it if it is affected.

What it is: CVE-2026-90161 is a high-severity 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-2026-90161 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-2026-90161/ (Markdown: https://insights.sbomify.com/CVE-2026-90161/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90161
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90161
- OSV: https://osv.dev/vulnerability/CVE-2026-90161

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90161/
Summaries are generated and may contain mistakes; the official description above is the record.