#VU9520 Race condition in Linux kernel - CVE-2017-1000405

Vulnerability identifier: #VU9520

Vulnerability risk: Low

CVSSv4.0: 5.4 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2017-1000405

CWE-ID: CWE-362

Exploitation vector: Local

Exploit availability: Yes

Vulnerable software:
Linux kernel
Operating systems & Components / Operating system

Vendor: Linux Foundation

Description

The vulnerability allows a local user to perform a denial of service (DoS) attack.

The vulnerability exists due to a race condition within touch_pmd() function in mmhugemem.c file when handling THPs. A local user can read read-only huge pages using the get_user_pages() function and overwrite arbitrary huge pages and files mapped via THP.

Successful exploitation of the vulnerability may allow an attacker to perform a denial of service (DoS) attack.

This vulnerability is a result of patch against a another privilege escalation vulnerability in Linux kernel known as Dirty Cow (CVE-2016-5195).

Mitigation
Install a patch from vendor's repository:
https://github.com/torvalds/linux/commit/a8f97366452ed491d13cf1e44241bc0b5740b1f0

Vulnerable software versions

Linux kernel: 2.6.38 - 2.6.39.4, 4.0 - 4.0.9, 4.1 - 4.14, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9

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External links
https://github.com/torvalds/linux/commit/a8f97366452ed491d13cf1e44241bc0b5740b1f0

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Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.