# CVE-2026-45837: bpf: Fix use-after-free in arena_vm_close on fork

> A use-after-free in the Linux kernel BPF arena allows attackers to execute arbitrary code or escalate privileges via fork and memory operations.

- **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:** 27 May 2026
- **Updated:** 14 Jun 2026
- **Also known as:** BELL-CVE-2026-45837, DEBIAN-CVE-2026-45837, GHSA-5vq6-7cj2-4m9j, UBUNTU-CVE-2026-45837

## What is CVE-2026-45837?

CVE-2026-45837 is a high-severity use after free vulnerability in Linux kernel, published on 27 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:

bpf: Fix use-after-free in arena_vm_close on fork

arena_vm_open() only bumps vml->mmap_count but never registers the
child VMA in arena->vma_list. The vml->vma always points at the
parent VMA, so after parent munmap the pointer dangles. If the child
then calls bpf_arena_free_pages(), zap_pages() reads the stale
vml->vma triggering use-after-free.

Fix this by preventing the arena VMA from being inherited across
fork with VM_DONTCOPY, and preventing VMA splits via the may_split
callback.

Also reject mremap with a .mremap callback returning -EINVAL. A
same-size mremap(MREMAP_FIXED) on the full arena VMA reaches
copy_vma() through the following path:

  check_prep_vma()       - returns 0 early: new_len == old_len
                           skips VM_DONTEXPAND check
  prep_move_vma()        - vm_start == old_addr and
                           vm_end == old_addr + old_len
                           so may_split is never called
  move_vma()
    copy_vma_and_data()
      copy_vma()
        vm_area_dup()    - copies vm_private_data (vml pointer)
        vm_ops->open()   - bumps vml->mmap_count
      vm_ops->mremap()   - returns -EINVAL, rollback unmaps new VMA

The refcount ensures the rollback's arena_vm_close does not free
the vml shared with the original VMA.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-45837?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-45837?

Apply the vendor's patch.

## Is CVE-2026-45837 being exploited?

There is no known exploitation of CVE-2026-45837 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-2026-45837 and fix it if it is affected.

What it is: CVE-2026-45837 is a high-severity use after free vulnerability in Linux kernel, published on 27 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-2026-45837 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-2026-45837/ (Markdown: https://insights.sbomify.com/CVE-2026-45837/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45837
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45837
- OSV: https://osv.dev/vulnerability/CVE-2026-45837

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45837/
Summaries are generated and may contain mistakes; the official description above is the record.