MacOS Insecure Swap File

2017.05.18

Credit: ianbeer

Risk: Low

Local: Yes

Remote: No

CVE: CVE-2017-2494

CWE: N/A

CVSS Base Score: 9.3/10

Impact Subscore: 10/10

Exploitability Subscore: 8.6/10

Exploit range: Remote

Attack complexity: Medium

Authentication: No required

Confidentiality impact: Complete

Integrity impact: Complete

Availability impact: Complete

 MacOS uses an insecure swap file
CVE-2017-2494
This came out of a discussion with Jann Horn this afternoon; credit is his.
It turns out that even with SIP enabled a regular root user can write to the swapfile under /private/var/vm/swapfile0.
That file is created on demand when the system starts to swap; if you can't see it increase system load.
Then as root (with SIP enabled) do:
cat /dev/urandom > /private/var/vm/swapfile0
We observed multiple interesting-looking kernel panics including in the swapfile decompression code and also the intel GPU driver doing something with GPU pages.
Found by: ianbeer

See this note in RAW Version

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MacOS Insecure Swap File

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