# CVE-2025-39836: efi: stmm: Fix incorrect buffer allocation method

> Incorrect buffer allocation in the Linux kernel EFI STMM driver can cause memory corruption, potentially leading to code execution or system crashes.

- **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:** 16 Sep 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-39836, DEBIAN-CVE-2025-39836, GHSA-64pc-rqj8-96w6, ROOT-OS-DEBIAN-13-CVE-2025-39836, ROOT-OS-UBUNTU-2404-CVE-2025-39836, UBUNTU-CVE-2025-39836

## What is CVE-2025-39836?

CVE-2025-39836 is a high-severity memory corruption vulnerability in Linux kernel, published on 16 Sep 2025. 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:

efi: stmm: Fix incorrect buffer allocation method

The communication buffer allocated by setup_mm_hdr() is later on passed
to tee_shm_register_kernel_buf(). The latter expects those buffers to be
contiguous pages, but setup_mm_hdr() just uses kmalloc(). That can cause
various corruptions or BUGs, specifically since commit 9aec2fb0fd5e
("slab: allocate frozen pages"), though it was broken before as well.

Fix this by using alloc_pages_exact() instead of kmalloc().

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2025-39836?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-39836?

Apply the vendor's patch.

## Is CVE-2025-39836 being exploited?

There is no known exploitation of CVE-2025-39836 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-2025-39836 and fix it if it is affected.

What it is: CVE-2025-39836 is a high-severity memory corruption vulnerability in Linux kernel, published on 16 Sep 2025. 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-2025-39836 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-2025-39836/ (Markdown: https://insights.sbomify.com/CVE-2025-39836/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-39836
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-39836
- OSV: https://osv.dev/vulnerability/CVE-2025-39836

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-39836/
Summaries are generated and may contain mistakes; the official description above is the record.