Apple macOS/iOS - NSUnarchiver Heap Corruption Due to Lack of Bounds Checking in [NSBuiltinCharacterSet initWithCoder:]

Author: Google Security Research
type: dos
platform: multiple
port: 
date_added: 2017-05-23 
date_updated: 2017-12-16 
verified: 1 
codes: CVE-2017-2523;HT207798;HT207797 
tags: 
aliases:  
screenshot_url:  
application_url: 

Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1170

Via NSUnarchiver we can read NSBuiltinCharacterSet with a controlled serialized state.
It reads a controlled int using decodeValueOfObjCType:"i" then either passes it to
CFCharacterSetGetPredefined or uses it directly to manipulate __NSBuiltinSetTable.
Neither path has any bounds checking and the index is used to maniupulate c arrays of pointers.

Attached python script will generate a serialized NSBuiltinCharacterSet with a value of 42
for the character set identifier.

tested on MacOS 10.12.3 (16D32)


Proof of Concept:
https://gitlab.com/exploit-database/exploitdb-bin-sploits/-/raw/main/bin-sploits/42050.zip