# CVE-2025-40353: arm64: mte: Do not warn if the page is already tagged in copy_highpage()

> A kernel bug causes unnecessary warnings during memory migration, potentially leading to system instability or denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-40353, DEBIAN-CVE-2025-40353, GHSA-27p4-p9vc-8f94, ROOT-OS-UBUNTU-2204-CVE-2025-40353, ROOT-OS-UBUNTU-2404-CVE-2025-40353, UBUNTU-CVE-2025-40353

## What is CVE-2025-40353?

CVE-2025-40353 is a denial of service vulnerability in Linux, published on 16 Dec 2025. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

arm64: mte: Do not warn if the page is already tagged in copy_highpage()

The arm64 copy_highpage() assumes that the destination page is newly
allocated and not MTE-tagged (PG_mte_tagged unset) and warns
accordingly. However, following commit 060913999d7a ("mm: migrate:
support poisoned recover from migrate folio"), folio_mc_copy() is called
before __folio_migrate_mapping(). If the latter fails (-EAGAIN), the
copy will be done again to the same destination page. Since
copy_highpage() already set the PG_mte_tagged flag, this second copy
will warn.

Replace the WARN_ON_ONCE(page already tagged) in the arm64
copy_highpage() with a comment.

## Which versions are affected by CVE-2025-40353?


## How do I fix CVE-2025-40353?

Apply the vendor's patch.

## Is CVE-2025-40353 being exploited?

There is no known exploitation of CVE-2025-40353 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40353 and fix it if it is affected.

What it is: CVE-2025-40353 is a denial of service vulnerability in Linux, published on 16 Dec 2025. 
Exploitation: There is no known exploitation of CVE-2025-40353 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-2025-40353/ (Markdown: https://insights.sbomify.com/CVE-2025-40353/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40353
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40353
- OSV: https://osv.dev/vulnerability/CVE-2025-40353

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40353/
Summaries are generated and may contain mistakes; the official description above is the record.