# CVE-2025-68179: s390: Disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP

> Enabling HugeTLB Vmemmap Optimization on s390 causes kernel crashes due to improper TLB flushing, leading to denial of service.

- **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:** 16 Dec 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-68179, DEBIAN-CVE-2025-68179, GHSA-2v94-v9cc-qp7h, ROOT-OS-DEBIAN-13-CVE-2025-68179, ROOT-OS-UBUNTU-2404-CVE-2025-68179, UBUNTU-CVE-2025-68179

## What is CVE-2025-68179?

CVE-2025-68179 is a high-severity denial of service vulnerability in Linux, published on 16 Dec 2025. 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:

s390: Disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP

As reported by Luiz Capitulino enabling HVO on s390 leads to reproducible
crashes. The problem is that kernel page tables are modified without
flushing corresponding TLB entries.

Even if it looks like the empty flush_tlb_all() implementation on s390 is
the problem, it is actually a different problem: on s390 it is not allowed
to replace an active/valid page table entry with another valid page table
entry without the detour over an invalid entry. A direct replacement may
lead to random crashes and/or data corruption.

In order to invalidate an entry special instructions have to be used
(e.g. ipte or idte). Alternatively there are also special instructions
available which allow to replace a valid entry with a different valid
entry (e.g. crdte or cspg).

Given that the HVO code currently does not provide the hooks to allow for
an implementation which is compliant with the s390 architecture
requirements, disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP again, which is
basically a revert of the original patch which enabled it.

## Which versions are affected by CVE-2025-68179?


## How do I fix CVE-2025-68179?

Apply the vendor's patch.

## Is CVE-2025-68179 being exploited?

There is no known exploitation of CVE-2025-68179 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68179 and fix it if it is affected.

What it is: CVE-2025-68179 is a high-severity denial of service vulnerability in Linux, published on 16 Dec 2025. 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-2025-68179 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-2025-68179/ (Markdown: https://insights.sbomify.com/CVE-2025-68179/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68179
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68179
- OSV: https://osv.dev/vulnerability/CVE-2025-68179

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68179/
Summaries are generated and may contain mistakes; the official description above is the record.