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.
Published 2017-11-30 22:29:00
Updated 2023-06-26 16:55:43
Source MITRE
View at NVD,   CVE.org

Exploit prediction scoring system (EPSS) score for CVE-2017-1000405

0.18%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 54 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2017-1000405

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
6.9
MEDIUM AV:L/AC:M/Au:N/C:C/I:C/A:C
3.4
10.0
NIST
7.0
HIGH CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
1.0
5.9
NIST
7.0
HIGH CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
1.0
5.9
NIST

CWE ids for CVE-2017-1000405

References for CVE-2017-1000405

Products affected by CVE-2017-1000405

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