# CVE-2026-74600: mm/page_table_check: skip special zero mappings

> An unprivileged local user can trigger a kernel crash by overflowing file_map_count via special zero mappings in the page table checker.

- **Severity:** Not scored
- **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:** 22 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2026-74600, DEBIAN-CVE-2026-74600, GHSA-mr2c-gwqw-3x39, UBUNTU-CVE-2026-74600

## What is CVE-2026-74600?

CVE-2026-74600 is a denial of service vulnerability in Linux, published on 22 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/page_table_check: skip special zero mappings

page_table_check_set() and page_table_check_clear() account mappings based
on PageAnon().  Shared zero-page PTEs and huge zero PMDs are special
mappings, but page_table_check can still account them as file-backed
pages.

An unprivileged process can populate enough zero mappings to overflow
file_map_count and hit the existing BUG_ON().  The PTE path can do this
with the shared zero page, and the PMD path can do the same with huge zero
mappings.

Skip special zero mappings in the user page-table accounting paths.  Keep
the PTE-side pte_special() check, and identify huge zero PMDs from the
mapped folio instead of pmd_special().  That covers architectures where
pmd_special() is a no-op without adding huge_zero_pfn checks to the
generic counter helpers.

## Which versions are affected by CVE-2026-74600?


## How do I fix CVE-2026-74600?

Apply the vendor's patch.

## Is CVE-2026-74600 being exploited?

There is no known exploitation of CVE-2026-74600 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74600 and fix it if it is affected.

What it is: CVE-2026-74600 is a denial of service vulnerability in Linux, published on 22 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-2026-74600 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-2026-74600/ (Markdown: https://insights.sbomify.com/CVE-2026-74600/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74600
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74600
- OSV: https://osv.dev/vulnerability/CVE-2026-74600

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74600/
Summaries are generated and may contain mistakes; the official description above is the record.