# CVE-2026-63911: xfrm: iptfs: reset runtime state when cloning SAs

> A use-after-free vulnerability in the Linux kernel's IPTFS module allows attackers to cause denial of service or potentially execute code via crafted network packets.

- **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:** 19 Jul 2026
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2026-63911, DEBIAN-CVE-2026-63911, GHSA-3gc2-w5w2-ffch, UBUNTU-CVE-2026-63911

## What is CVE-2026-63911?

CVE-2026-63911 is a high-severity use after free vulnerability in Linux, published on 19 Jul 2026. 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:

xfrm: iptfs: reset runtime state when cloning SAs

iptfs_clone_state() clones the IPTFS mode data with kmemdup(). This
copies runtime objects which must not be shared with the original SA,
including the embedded sk_buff_head, hrtimers, spinlock, and in-flight
reassembly/reorder state.

If xfrm_state_migrate() fails after clone_state() but before the later
init_state() call has reinitialized those fields, the cloned state can be
destroyed by xfrm_state_gc_task() with list and timer state copied from the
original SA. With queued packets this lets the clone splice and free skbs
owned by the original IPTFS queue, leading to use-after-free and
double-free reports in iptfs_destroy_state() and skb release paths.

Reinitialize the clone's runtime state before publishing it through
x->mode_data. Because clone_state() now publishes a destroyable mode_data
object before init_state(), take the mode callback module reference there.
Avoid taking it again from __iptfs_init_state() for the same object.

## Which versions are affected by CVE-2026-63911?


## How do I fix CVE-2026-63911?

Apply the vendor's patch.

## Is CVE-2026-63911 being exploited?

There is no known exploitation of CVE-2026-63911 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63911 and fix it if it is affected.

What it is: CVE-2026-63911 is a high-severity use after free vulnerability in Linux, published on 19 Jul 2026. 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-2026-63911 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-2026-63911/ (Markdown: https://insights.sbomify.com/CVE-2026-63911/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63911
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63911
- OSV: https://osv.dev/vulnerability/CVE-2026-63911

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63911/
Summaries are generated and may contain mistakes; the official description above is the record.