MacOS Insecure Swap File

2017.05.18
Credit: ianbeer
Risk: Low
Local: Yes
Remote: No
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


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