# CVE-2026-63919: xfrm: input: hold netns during deferred transport reinjection

> A use-after-free vulnerability in the Linux kernel's xfrm input handling allows attackers to cause denial of service or potentially execute code via deferred transport reinjection.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 19 Jul 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-63919, DEBIAN-CVE-2026-63919, GHSA-c9j4-h9xp-p2mj, ROOT-OS-UBUNTU-2204-CVE-2026-63919, UBUNTU-CVE-2026-63919

## What is CVE-2026-63919?

CVE-2026-63919 is a high-severity use after free vulnerability in Linux kernel, published on 19 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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

xfrm: input: hold netns during deferred transport reinjection

Transport-mode reinjection stores a struct net pointer in skb->cb and
uses it later from xfrm_trans_reinject(). That pointer must stay valid
until the deferred callback runs.

Take a netns reference when queueing deferred reinjection work and drop
it after the callback completes. Use maybe_get_net() so the queueing
path does not revive a namespace that is already being torn down.

This keeps the existing workqueue design and fixes the netns lifetime
handling in one place for all users of xfrm_trans_queue_net().

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-63919?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-63919?

Apply the vendor's patch.

## Is CVE-2026-63919 being exploited?

There is no known exploitation of CVE-2026-63919 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63919 and fix it if it is affected.

What it is: CVE-2026-63919 is a high-severity use after free vulnerability in Linux kernel, published on 19 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-63919 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-63919/ (Markdown: https://insights.sbomify.com/CVE-2026-63919/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63919
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63919
- OSV: https://osv.dev/vulnerability/CVE-2026-63919

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63919/
Summaries are generated and may contain mistakes; the official description above is the record.