# CVE-2023-53338: lwt: Fix return values of BPF xmit ops

> A use-after-free vulnerability in the Linux kernel's BPF xmit operations allows attackers to cause kernel crashes or potentially execute code.

- **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:** 17 Sep 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2023-53338, DEBIAN-CVE-2023-53338, GHSA-wqfp-wxf7-9vr7, UBUNTU-CVE-2023-53338

## What is CVE-2023-53338?

CVE-2023-53338 is a critical use after free vulnerability in Linux kernel, published on 17 Sep 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:

lwt: Fix return values of BPF xmit ops

BPF encap ops can return different types of positive values, such like
NET_RX_DROP, NET_XMIT_CN, NETDEV_TX_BUSY, and so on, from function
skb_do_redirect and bpf_lwt_xmit_reroute. At the xmit hook, such return
values would be treated implicitly as LWTUNNEL_XMIT_CONTINUE in
ip(6)_finish_output2. When this happens, skbs that have been freed would
continue to the neighbor subsystem, causing use-after-free bug and
kernel crashes.

To fix the incorrect behavior, skb_do_redirect return values can be
simply discarded, the same as tc-egress behavior. On the other hand,
bpf_lwt_xmit_reroute returns useful errors to local senders, e.g. PMTU
information. Thus convert its return values to avoid the conflict with
LWTUNNEL_XMIT_CONTINUE.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2023-53338?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2023-53338?

Apply the vendor's patch.

## Is CVE-2023-53338 being exploited?

There is no known exploitation of CVE-2023-53338 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-2023-53338 and fix it if it is affected.

What it is: CVE-2023-53338 is a critical use after free vulnerability in Linux kernel, published on 17 Sep 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-2023-53338 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-2023-53338/ (Markdown: https://insights.sbomify.com/CVE-2023-53338/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-53338
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-53338
- OSV: https://osv.dev/vulnerability/CVE-2023-53338

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-53338/
Summaries are generated and may contain mistakes; the official description above is the record.