# CVE-2026-23415: futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy()

> A race condition in the Linux kernel futex subsystem 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:** 2 Apr 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-23415, DEBIAN-CVE-2026-23415, GHSA-chr7-rqmr-q86r, UBUNTU-CVE-2026-23415

## What is CVE-2026-23415?

CVE-2026-23415 is a high-severity use after free vulnerability in Linux kernel, published on 2 Apr 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:

futex: Fix UaF between futex_key_to_node_opt() and vma_replace_policy()

During futex_key_to_node_opt() execution, vma->vm_policy is read under
speculative mmap lock and RCU. Concurrently, mbind() may call
vma_replace_policy() which frees the old mempolicy immediately via
kmem_cache_free().

This creates a race where __futex_key_to_node() dereferences a freed
mempolicy pointer, causing a use-after-free read of mpol->mode.

[  151.412631] BUG: KASAN: slab-use-after-free in __futex_key_to_node (kernel/futex/core.c:349)
[  151.414046] Read of size 2 at addr ffff888001c49634 by task e/87

[  151.415969] Call Trace:

[  151.416732]  __asan_load2 (mm/kasan/generic.c:271)
[  151.416777]  __futex_key_to_node (kernel/futex/core.c:349)
[  151.416822]  get_futex_key (kernel/futex/core.c:374 kernel/futex/core.c:386 kernel/futex/core.c:593)

Fix by adding rcu to __mpol_put().

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-23415?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23415?

Apply the vendor's patch.

## Is CVE-2026-23415 being exploited?

There is no known exploitation of CVE-2026-23415 in the wild and no public exploit code.

Public exploit code:

- https://github.com/addman2/uaf-exploit-cve-2026-23415 (github_poc): https://github.com/addman2/uaf-exploit-cve-2026-23415

## 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-2026-23415 and fix it if it is affected.

What it is: CVE-2026-23415 is a high-severity use after free vulnerability in Linux kernel, published on 2 Apr 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-2026-23415 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-2026-23415/ (Markdown: https://insights.sbomify.com/CVE-2026-23415/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23415
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23415
- OSV: https://osv.dev/vulnerability/CVE-2026-23415

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23415/
Summaries are generated and may contain mistakes; the official description above is the record.