Google Chrome’s security lead and engineering director, Justin Schuh, has warned that users of the most popular web browser should update “like right this minute.” Why the urgency? Simply put, there is a zero-day vulnerability for Chrome that the Google Threat Analysis Group has determined is being actively exploited in the wild. What does that all mean? Well, a vulnerability is just a bug or flaw in the code and while they all need to be fixed, not all of them either can be or are being exploited. A zero-day vulnerability is one that threat actors have managed to create an exploit for, a way of doing bad things to your device or data, before the good guys even knew the vulnerability existed. In other words they have zero days in which to issue a fix. The bad news for users of Google Chrome is that this particular zero-day vulnerability, CVE-2019-5786, is already being exploited by the bad guys. Which is why it’s so important to make sure your browser has been updated to the latest patched version that fixes the vulnerability.
The problem explained
Although information regarding CVE-2019-5786 remains scarce currently, Satnam Narang, a senior research engineer at Tenable, says it is a “Use-After-Free (UAF) vulnerability in FileReader, an application programming interface (API) included in browsers to allow web applications to read the contents of files stored on a user’s computer.” Some further digging by Catalin Cimpanu over at ZDNet suggests that there are malicious PDF files in the wild that are being used to exploit this vulnerability. “The PDF documents would contact a remote domain with information on the users’ device –such as IP address, OS version, Chrome version, and the path of the PDF file on the user’s computer” Cimpanu says. These could just be used for tracking purposes, but there is also the potential for more malicious behavior. The ‘use-after-free’ vulnerability is a memory corruption flaw that carries the risk of escalated privileges on a machine where a threat actor has modified data in memory through exploiting it. That’s why Google has issued the urgent update warning, as the potential is there for exploits to be crafted that could enable an attacker to remotely run arbitrary code (a remote code execution attack) whilst escaping the browser’s built-in sandbox protection.
What to do next
Luckily this is an easy problem to fix, just make sure you do it as soon as you’ve finished reading this! First, head over to the drop-down menu in Chrome (you’ll find it at the far right of the toolbar – click on the three stacked dots) and select Help|About Google Chrome. You could also type chrome://settings/help in the address bar if you prefer, which takes you to the same dialog box. This will tell you if you have the current version running or if there is an update available. To be safe from this zero-day exploit, make sure that it says you are running version 72.0.3626.121 (Official Build). If not, then Chrome should go and fetch the latest version and update your browser for you automatically.