# CVE-2026-53239: xfrm: policy: fix use-after-free on inexact bin in xfrm_policy_bysel_ctx()

> A race condition in the Linux kernel's xfrm policy handling allows a use-after-free, potentially enabling local attackers to execute code or escalate privileges.

- **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:** 25 Jun 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-90842, BELL-CVE-2026-53239, DEBIAN-CVE-2026-53239, GHSA-qmj7-fh92-4787, ROOT-OS-DEBIAN-11-CVE-2026-53239, ROOT-OS-DEBIAN-12-CVE-2026-53239, ROOT-OS-UBUNTU-2204-CVE-2026-53239, ROOT-OS-UBUNTU-2404-CVE-2026-53239, UBUNTU-CVE-2026-53239

## What is CVE-2026-53239?

CVE-2026-53239 is a high-severity use after free vulnerability in Linux kernel, published on 25 Jun 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: policy: fix use-after-free on inexact bin in xfrm_policy_bysel_ctx()

Fix the race by pruning the bin while still holding xfrm_policy_lock,
before dropping it. Use __xfrm_policy_inexact_prune_bin() directly since
the lock is already held. The wrapper xfrm_policy_inexact_prune_bin()
becomes unused and is removed.

Race:

  CPU0 (XFRM_MSG_DELPOLICY)           CPU1 (XFRM_MSG_NEWSPDINFO)
  ==========================          ==========================
  xfrm_policy_bysel_ctx():
    spin_lock_bh(xfrm_policy_lock)
    bin = xfrm_policy_inexact_lookup()
    __xfrm_policy_unlink(pol)
    spin_unlock_bh(xfrm_policy_lock)
    xfrm_policy_kill(ret)
    // wide window, lock not held
                                       xfrm_hash_rebuild():
                                         spin_lock_bh(xfrm_policy_lock)
                                         __xfrm_policy_inexact_flush():
                                           kfree_rcu(bin)  // bin freed
                                         spin_unlock_bh(xfrm_policy_lock)
    xfrm_policy_inexact_prune_bin(bin)
    // UAF: bin is freed

Weakness: CWE-416 (Use After Free), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2026-53239?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-53239?

Apply the vendor's patch.

## Is CVE-2026-53239 being exploited?

There is no known exploitation of CVE-2026-53239 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-2026-53239 and fix it if it is affected.

What it is: CVE-2026-53239 is a high-severity use after free vulnerability in Linux kernel, published on 25 Jun 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-2026-53239 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-2026-53239/ (Markdown: https://insights.sbomify.com/CVE-2026-53239/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53239
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53239
- OSV: https://osv.dev/vulnerability/CVE-2026-53239

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-53239/
Summaries are generated and may contain mistakes; the official description above is the record.