# CVE-2026-64253: kernel/fork: clear PF_BLOCK_TS in copy_process()

> A null pointer dereference in the Linux kernel fork process can cause a system crash, requiring a kernel patch to fix.

- **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:** 24 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-64253, DEBIAN-CVE-2026-64253, GHSA-3p6p-hf89-xh98, ROOT-OS-UBUNTU-2204-CVE-2026-64253, UBUNTU-CVE-2026-64253

## What is CVE-2026-64253?

CVE-2026-64253 is a medium-severity vulnerability in Linux kernel, published on 24 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:

kernel/fork: clear PF_BLOCK_TS in copy_process()

PF_BLOCK_TS is only set in blk_time_get_ns() when current->plug is
non-NULL, and blk_finish_plug() clears it via __blk_flush_plug()
before NULLing the plug pointer.  copy_process() breaks the
invariant by inheriting PF_BLOCK_TS from the parent while resetting
the child's plug to NULL.

Clear PF_BLOCK_TS alongside that assignment so callers can rely on
"PF_BLOCK_TS set implies current->plug != NULL" and dereference
current->plug unguarded.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-64253?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64253?

Apply the vendor's patch.

## Is CVE-2026-64253 being exploited?

There is no known exploitation of CVE-2026-64253 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-2026-64253 and fix it if it is affected.

What it is: CVE-2026-64253 is a medium-severity vulnerability in Linux kernel, published on 24 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-2026-64253 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-2026-64253/ (Markdown: https://insights.sbomify.com/CVE-2026-64253/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64253
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64253
- OSV: https://osv.dev/vulnerability/CVE-2026-64253

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64253/
Summaries are generated and may contain mistakes; the official description above is the record.