# CVE-2026-80718: mm/percpu-km: fix bitmap overflow and accounting in pcpu_create_chunk()

> A buffer overflow in the Linux kernel's percpu memory management allows attackers to corrupt memory, potentially leading to system crashes or arbitrary code execution.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Aug 2026
- **Updated:** 29 Aug 2026
- **Also known as:** AZL-98138, BELL-CVE-2026-80718, DEBIAN-CVE-2026-80718, GHSA-wv7w-q623-9gwq, UBUNTU-CVE-2026-80718

## What is CVE-2026-80718?

CVE-2026-80718 is a high-severity memory corruption vulnerability in Linux, published on 28 Aug 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:

mm/percpu-km: fix bitmap overflow and accounting in pcpu_create_chunk()

In pcpu_create_chunk(), nr_pages is the total contiguous backing
allocation, i.e., nr_units * pcpu_unit_pages, but pcpu_chunk_populated()
uses it to set chunk->populated, whose size is pcpu_unit_pages, bitmap. 
Since bit N in chunk->populated means page offset N inside every unit is
backed.  When nr_units > 1, the function writes beyond chunk->populated. 
Fix it by using chunk->nr_pages.

It also fixes the global pcpu_nr_empty_pop_pages accounting, since
pcpu_balance_free() only iterates up to chunk->nr_pages.

Commit a63d4ac4ab609 ("percpu: make percpu-km set chunk->populated bitmap
properly") introduced the bitmap overflow issue.  Later, commit
b539b87fed37f ("percpu: implmeent pcpu_nr_empty_pop_pages and
chunk->nr_populated") added pcpu_nr_empty_pop_pages and caused the
accounting issue.

## Which versions are affected by CVE-2026-80718?


## How do I fix CVE-2026-80718?

Apply the vendor's patch.

## Is CVE-2026-80718 being exploited?

There is no known exploitation of CVE-2026-80718 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-80718 and fix it if it is affected.

What it is: CVE-2026-80718 is a high-severity memory corruption vulnerability in Linux, published on 28 Aug 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-2026-80718 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-2026-80718/ (Markdown: https://insights.sbomify.com/CVE-2026-80718/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-80718
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-80718
- OSV: https://osv.dev/vulnerability/CVE-2026-80718

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-80718/
Summaries are generated and may contain mistakes; the official description above is the record.