# CVE-2025-40074: ipv4: start using dst_dev_rcu()

> A use-after-free vulnerability in the Linux kernel IPv4 stack allows attackers to potentially execute code or escalate privileges.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 Oct 2025
- **Updated:** 3 Oct 2026
- **Also known as:** AZL-68894, BELL-CVE-2025-40074, DEBIAN-CVE-2025-40074, GHSA-g35w-4vfx-hjpg, ROOT-OS-DEBIAN-11-CVE-2025-40074, ROOT-OS-DEBIAN-12-CVE-2025-40074, ROOT-OS-DEBIAN-13-CVE-2025-40074, ROOT-OS-UBUNTU-2204-CVE-2025-40074, ROOT-OS-UBUNTU-2404-CVE-2025-40074, UBUNTU-CVE-2025-40074

## What is CVE-2025-40074?

CVE-2025-40074 is a critical use after free vulnerability in Linux, published on 28 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

ipv4: start using dst_dev_rcu()

Change icmpv4_xrlim_allow(), ip_defrag() to prevent possible UAF.

Change ipmr_prepare_xmit(), ipmr_queue_fwd_xmit(), ip_mr_output(),
ipv4_neigh_lookup() to use lockdep enabled dst_dev_rcu().

## Which versions are affected by CVE-2025-40074?


## How do I fix CVE-2025-40074?

Apply the vendor's patch.

## Is CVE-2025-40074 being exploited?

There is no known exploitation of CVE-2025-40074 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40074 and fix it if it is affected.

What it is: CVE-2025-40074 is a critical use after free vulnerability in Linux, published on 28 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-40074 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-2025-40074/ (Markdown: https://insights.sbomify.com/CVE-2025-40074/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40074
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40074
- OSV: https://osv.dev/vulnerability/CVE-2025-40074

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40074/
Summaries are generated and may contain mistakes; the official description above is the record.