# CVE-2026-64295: mm: page_ext: add count limit to page_ext_iter_next to prevent invalid PFN access

> A NULL pointer dereference in the Linux kernel memory management subsystem can cause a system crash during memory hotplug operations.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-64295, DEBIAN-CVE-2026-64295, GHSA-v5hf-7896-cmm7, ROOT-OS-UBUNTU-2204-CVE-2026-64295, UBUNTU-CVE-2026-64295

## What is CVE-2026-64295?

CVE-2026-64295 is a medium-severity vulnerability in Linux kernel, published on 25 Jul 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:

mm: page_ext: add count limit to page_ext_iter_next to prevent invalid PFN access

The page_ext iteration API does not validate if the PFN still belongs to a
valid section while advancing the iterator.  When dynamically adding
memory in the hotplug path, it can lead to a NULL pointer dereference
during page_ext_lookup at the boundary of the last valid section when
iterator count equals __pgcount.

The for_each_page_ext() macro calls page_ext_iter_next() as its loop
increment.  for_each_page_ext() does a "__page_ext =
page_ext_iter_next(&__iter)" at the end.  This causes page_ext_iter_next()
to increment iter->index past __pgcount and call page_ext_lookup(start_pfn
+ __pgcount).  During memory hotplug (online), the PFN at start_pfn +
__pgcount may belong to a section that has not yet been initialized,
causing page_ext_lookup() to trigger a NULL pointer dereference.

[   14.555124][  T846] Call trace:
[   14.555125][  T846]  lookup_page_ext+0x6c/0x108 (P)
[   14.555127][  T846]  page_ext_lookup+0x30/0x3c
[   14.555129][  T846]  __reset_page_owner+0x11c/0x260
[   14.571201][  T846]  __free_pages_ok+0x5e8/0x8e0
[   14.571204][  T846]  __free_pages_core+0x78/0xf0
[   14.571206][  T846]  generic_online_page+0x14/0x24
[   14.597782][  T846]  online_pages+0x178/0x30c
[   14.597784][  T846]  memory_block_change_state+0x284/0x32c
[   14.597787][  T846]  memory_subsys_online+0x4c/0x64
[   14.597789][  T846]  device_online+0x88/0xb0
[   14.597791][  T846]  online_memory_block+0x30/0x40
[   14.597793][  T846]  walk_memory_blocks+0xac/0xe8
[   14.597794][  T846]  add_memory_resource+0x280/0x298
[   14.656161][  T846]  add_memory+0x60/0x98

Move the iteration boundary enforcement inside the iterator functions, so
callers cannot inadvertently access beyond the requested range.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-64295?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64295?

Apply the vendor's patch.

## Is CVE-2026-64295 being exploited?

There is no known exploitation of CVE-2026-64295 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-2026-64295 and fix it if it is affected.

What it is: CVE-2026-64295 is a medium-severity vulnerability in Linux kernel, published on 25 Jul 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-2026-64295 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-2026-64295/ (Markdown: https://insights.sbomify.com/CVE-2026-64295/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64295
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64295
- OSV: https://osv.dev/vulnerability/CVE-2026-64295

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64295/
Summaries are generated and may contain mistakes; the official description above is the record.