# CVE-2026-89718: zram: fix out-of-bounds access in writeback_store()

> A race condition in the Linux kernel zram module allows local attackers to trigger out-of-bounds memory access, potentially leading to code execution or privilege escalation.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-100151, BELL-CVE-2026-89718, DEBIAN-CVE-2026-89718, GHSA-8g3j-f4r3-9992, UBUNTU-CVE-2026-89718

## What is CVE-2026-89718?

CVE-2026-89718 is a vulnerability in Linux, published on 11 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:

zram: fix out-of-bounds access in writeback_store()

Patch series "zram: fix stale scan bounds after reinitialization".

Both writeback_store() and read_block_state() derive their table scan
bounds from zram->disksize before acquiring dev_lock.  If the device is
reset and reinitialized with a smaller disksize between that read and lock
acquisition, the bound can describe the old table while the scan operates
on the new one.  This can lead to out-of-bounds slot accesses.

Move both bound calculations under dev_lock so each bound remains
consistent with the table throughout its scan.  Keep the fixes separate
because the affected interfaces originate from different commits and can
be backported independently.

This patch (of 2):

writeback_store() calculates the table scan bounds before taking dev_lock.
A reset followed by reconfiguration with a smaller disksize can therefore
replace zram->table while writeback_store() is waiting for the lock.  Once
it acquires the lock, it sees an initialized device but scans the new
table using the old upper bound, resulting in an out-of-bounds access.

Calculate the number of pages while holding dev_lock so the scan bound
matches the table protected by the lock.

## Which versions are affected by CVE-2026-89718?


## How do I fix CVE-2026-89718?

Apply the vendor's patch.

## Is CVE-2026-89718 being exploited?

There is no known exploitation of CVE-2026-89718 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89718 and fix it if it is affected.

What it is: CVE-2026-89718 is a vulnerability in Linux, published on 11 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-2026-89718 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-2026-89718/ (Markdown: https://insights.sbomify.com/CVE-2026-89718/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89718
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89718
- OSV: https://osv.dev/vulnerability/CVE-2026-89718

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89718/
Summaries are generated and may contain mistakes; the official description above is the record.