# CVE-2025-40174: x86/mm: Fix SMP ordering in switch_mm_irqs_off()

> A race condition in the Linux kernel x86 memory management allows attackers to bypass TLB flushes, potentially leading to information disclosure or privilege escalation.

- **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:** 12 Nov 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-40174, DEBIAN-CVE-2025-40174, GHSA-m7p7-jwxv-mmf9, UBUNTU-CVE-2025-40174

## What is CVE-2025-40174?

CVE-2025-40174 is a high-severity vulnerability in Linux, published on 12 Nov 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:

x86/mm: Fix SMP ordering in switch_mm_irqs_off()

Stephen noted that it is possible to not have an smp_mb() between
the loaded_mm store and the tlb_gen load in switch_mm(), meaning the
ordering against flush_tlb_mm_range() goes out the window, and it
becomes possible for switch_mm() to not observe a recent tlb_gen
update and fail to flush the TLBs.

[ dhansen: merge conflict fixed by Ingo ]

## Which versions are affected by CVE-2025-40174?


## How do I fix CVE-2025-40174?

Apply the vendor's patch.

## Is CVE-2025-40174 being exploited?

There is no known exploitation of CVE-2025-40174 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40174 and fix it if it is affected.

What it is: CVE-2025-40174 is a high-severity vulnerability in Linux, published on 12 Nov 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-2025-40174 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-2025-40174/ (Markdown: https://insights.sbomify.com/CVE-2025-40174/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40174
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40174
- OSV: https://osv.dev/vulnerability/CVE-2025-40174

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40174/
Summaries are generated and may contain mistakes; the official description above is the record.