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CVE-2018-4121 - Safari Wasm Sections POC RCE Exploit

by MWR Labs (c) 2018

Details

• this proof of concept exploit targets Safari 11.0.3 (13604.5.6) on macOS 10.13.3 (17D47) versions only.
• compile the payload of your choice as a dylib with a constructor
• run python file_to_jsarray.py your.dylib payload.js
• serve this directory and point Safari to /exploit.html
• exploit is not fully reliable and uses hardcoded offsets for this macOS/Safari version.
• exploit takes a while to run due to the size of the heap spray (24.5GB).
• this issue is addressed in macOS 10.13.4 as CVE-2018-4121 (https://support.apple.com/en-gb/HT208692)

Credits

• Natalie Silvanovich of Google Project Zero - https://bugs.chromium.org/p/project-zero/issues/detail?id=1522
• Ian Beer of Google Project Zero - https://googleprojectzero.blogspot.co.uk/2014/07/pwn4fun-spring-2014-safari-part-i_24.html
• Phoenhex - https://phoenhex.re/
• Fermin Serna - https://media.blackhat.com/bh-us-12/Briefings/Serna/BH_US_12_Serna_Leak_Era_Slides.pdf

References

• https://labs.mwrinfosecurity.com/assets/BlogFiles/apple-safari-wasm-section-vuln-write-up-2018-04-16.pdf
• https://labs.mwrinfosecurity.com/mwr-vulnerability-disclosure-policy
• https://www.mwrinfosecurity.com/about-us/