# CVE-2026-43107: xfrm: account XFRMA_IF_ID in aevent size calculation

> A missing size calculation for XFRMA_IF_ID in the Linux kernel xfrm subsystem can cause a kernel panic via malformed netlink interactions.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 6 May 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-85869, BELL-CVE-2026-43107, DEBIAN-CVE-2026-43107, GHSA-v6vr-f94r-r434, ROOT-OS-DEBIAN-11-CVE-2026-43107, ROOT-OS-DEBIAN-12-CVE-2026-43107, ROOT-OS-UBUNTU-2204-CVE-2026-43107, ROOT-OS-UBUNTU-2404-CVE-2026-43107, UBUNTU-CVE-2026-43107

## What is CVE-2026-43107?

CVE-2026-43107 is a medium-severity denial of service vulnerability in Linux kernel, published on 6 May 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: account XFRMA_IF_ID in aevent size calculation

xfrm_get_ae() allocates the reply skb with xfrm_aevent_msgsize(), then
build_aevent() appends attributes including XFRMA_IF_ID when x->if_id is
set.

xfrm_aevent_msgsize() does not include space for XFRMA_IF_ID. For states
with if_id, build_aevent() can fail with -EMSGSIZE and hit BUG_ON(err < 0)
in xfrm_get_ae(), turning a malformed netlink interaction into a kernel
panic.

Account XFRMA_IF_ID in the size calculation unconditionally and replace
the BUG_ON with normal error unwinding.

Weakness: CWE-131 (Incorrect Calculation of Buffer Size)

## Which versions are affected by CVE-2026-43107?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43107?

Apply the vendor's patch.

## Is CVE-2026-43107 being exploited?

There is no known exploitation of CVE-2026-43107 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-2026-43107 and fix it if it is affected.

What it is: CVE-2026-43107 is a medium-severity denial of service vulnerability in Linux kernel, published on 6 May 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-2026-43107 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-2026-43107/ (Markdown: https://insights.sbomify.com/CVE-2026-43107/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43107
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43107
- OSV: https://osv.dev/vulnerability/CVE-2026-43107

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43107/
Summaries are generated and may contain mistakes; the official description above is the record.