Back in October 2019 we detected a classic watering-hole attack on a North Korea-related news site that exploited a chain of Google Chrome and Microsoft Windows zero-days. While we’ve already published blog posts briefly describing this operation (available here and here), in this blog post we’d like to take a deep technical dive into the exploits and vulnerabilities used in this attack.
Google Chrome remote code execution exploit
In the original blog post we described the exploit loader responsible for initial validation of the target and execution of the next stage JavaScript code containing the full browser exploit. The exploit is huge because, besides code, it contains byte arrays with shellcode, a Portable Executable (PE) file and WebAssembly (WASM) module used in the later stages of exploitation. The exploit abused a vulnerability in the WebAudio OfflineAudioContext interface and was targeting two release builds of Google Chrome 76.0.3809.87 and 77.0.3865.75. However, the vulnerability was introduced long before that and much earlier releases with a WebAudio component are also vulnerable. At the time of our discovery the current version of Google Chrome was 78, and while this version was also affected, the exploit did not support it and had a number of checks to ensure that it would only be executed on affected versions to prevent crashes. After our report, the vulnerability was assigned CVE-2019-13720 and was fixed in version 78.0.3904.87 with the following commit. A use-after-free (UAF) vulnerability, it could be triggered due to a ra ..
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