# CVE-2026-43091: xfrm: Wait for RCU readers during policy netns exit

> A use-after-free vulnerability in the Linux kernel's xfrm policy teardown allows attackers to cause denial of service or potentially execute code.

- **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:** 6 May 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-43091, DEBIAN-CVE-2026-43091, GHSA-jrph-46wx-r2g3, ROOT-OS-DEBIAN-11-CVE-2026-43091, ROOT-OS-DEBIAN-12-CVE-2026-43091, ROOT-OS-UBUNTU-2204-CVE-2026-43091, ROOT-OS-UBUNTU-2404-CVE-2026-43091, UBUNTU-CVE-2026-43091

## What is CVE-2026-43091?

CVE-2026-43091 is a high-severity use after free 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: Wait for RCU readers during policy netns exit

xfrm_policy_fini() frees the policy_bydst hash tables after flushing the
policy work items and deleting all policies, but it does not wait for
concurrent RCU readers to leave their read-side critical sections first.

The policy_bydst tables are published via rcu_assign_pointer() and are
looked up through rcu_dereference_check(), so netns teardown must also
wait for an RCU grace period before freeing the table memory.

Fix this by adding synchronize_rcu() before freeing the policy hash tables.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-43091?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43091?

Apply the vendor's patch.

## Is CVE-2026-43091 being exploited?

There is no known exploitation of CVE-2026-43091 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-2026-43091 and fix it if it is affected.

What it is: CVE-2026-43091 is a high-severity use after free 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-2026-43091 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-2026-43091/ (Markdown: https://insights.sbomify.com/CVE-2026-43091/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43091
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43091
- OSV: https://osv.dev/vulnerability/CVE-2026-43091

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43091/
Summaries are generated and may contain mistakes; the official description above is the record.