# CVE-2023-53559: ip_vti: fix potential slab-use-after-free in decode_session6

> A use-after-free vulnerability in the Linux kernel's ip_vti module allows attackers to cause denial of service or execute code when using specific queueing disciplines.

- **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:** 4 Oct 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2023-53559, DEBIAN-CVE-2023-53559, GHSA-6v4x-gf5x-r6w5, UBUNTU-CVE-2023-53559

## What is CVE-2023-53559?

CVE-2023-53559 is a high-severity use after free vulnerability in Linux kernel, published on 4 Oct 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:

ip_vti: fix potential slab-use-after-free in decode_session6

When ip_vti device is set to the qdisc of the sfb type, the cb field
of the sent skb may be modified during enqueuing. Then,
slab-use-after-free may occur when ip_vti device sends IPv6 packets.
As commit f855691975bb ("xfrm6: Fix the nexthdr offset in
_decode_session6.") showed, xfrm_decode_session was originally intended
only for the receive path. IP6CB(skb)->nhoff is not set during
transmission. Therefore, set the cb field in the skb to 0 before
sending packets.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2023-53559?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2023-53559?

Apply the vendor's patch.

## Is CVE-2023-53559 being exploited?

There is no known exploitation of CVE-2023-53559 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-2023-53559 and fix it if it is affected.

What it is: CVE-2023-53559 is a high-severity use after free vulnerability in Linux kernel, published on 4 Oct 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-2023-53559 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-2023-53559/ (Markdown: https://insights.sbomify.com/CVE-2023-53559/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53559
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53559
- OSV: https://osv.dev/vulnerability/CVE-2023-53559

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53559/
Summaries are generated and may contain mistakes; the official description above is the record.