Vulnerability in Linux Kernel

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 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.

Vulnerability class: Race Condition

EPSS: 0.028 (85.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.0 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

  • cve@mitre.org (VDB Entry, Third Party Advisory, vdb-entry, x_refsource_BID)
  • cve@mitre.org (x_refsource_REDHAT, vendor-advisory, Third Party Advisory)
  • cve@mitre.org (Exploit, Third Party Advisory, x_refsource_MISC, Issue Tracking)
  • cve@mitre.org (x_refsource_CONFIRM, Third Party Advisory)
  • cve@mitre.org (VDB Entry, Third Party Advisory, vdb-entry, x_refsource_SECTRACK)
  • cve@mitre.org (Exploit, VDB Entry, Third Party Advisory, exploit, Issue Tracking, x_refsource_EXPLOIT-DB)

Frequently asked questions

What is CVE-2017-1000405?
CVE-2017-1000405 is a high-severity vulnerability in Linux Kernel, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.0/10. Published 2017-11-30.
How severe is CVE-2017-1000405?
High severity. CVSS v3 base score is 7.0 out of 10.
Is CVE-2017-1000405 known to be exploited?
10 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.