Exploit

On April 12, a code commit[1] in Chromium get people’s attention. This is a bugfix for some vulnerability in Chromium Javascript engine v8. At the same time, the regression test case regress-1196683.js for this bugfix was also submitted. Based on this regression test case, some security researcher published an exploit sample[2]. Due to Chrome release pipeline, the vulnerability wasn’t been fixed in Chrome stable update until April 13[3]. Coincidentally, on April 15, another code commit[4] of some bugfix in v8 has also included one regression test case regress-1195777.js. Based on this test case, the exploit sample was exposed again[5]. Since the latest Chrome stable version does not pull this bugfix commit, the sample can still exploit in render process of latest Chrome. When the vulnerable Chormium browser accesses a malicious link without enabling the sandbox (–no-sandbox), the vulnerability will be triggered and caused remote code execution. ...

The general method of browser render process exploit is: after exploiting the vulnerability to obtain user mode arbitrary memory read/write primitive, the vtable of DOM/js object is tampered to hijack the code execution flow. Then VirtualProtect is called by ROP chain to modify the shellcode memory to PAGE_EXECUTE_READWRITE, and the code execution flow is jumped to shellcode by ROP chain finally. After Windows 8.1, Microsoft introduced CFG (Control Flow Guard)[1] mitigation to verify the indirect function call, which mitigates the exploitation of tampering with vtable to get code execution. ...