As Microsoft confirms a Google-disclosed and unpatched zero-day vulnerability is being targeted by attackers right now, here’s what you need to know.
Microsoft has confirmed that an unpatched ‘zero-day’ vulnerability in the Windows operating system, affecting every version from Windows 7 through to Windows 10, is being actively targeted. Microsoft was first informed of the vulnerability by Google’s Project Zero team, a dedicated unit comprised of leading vulnerability hunters, which tracks down these so-called zero-day security bugs. Because Project Zero had identified that the security problem was being actively exploited in the wild by attackers, it gave Microsoft a deadline of just seven days to fix it before disclosure. Microsoft failed to issue a security patch within that hugely restrictive timeframe, and Google went ahead and published details of the zero-day vulnerability, which is tracked as CVE-2020-17087.
The bug itself sits within the Windows Kernel Cryptography Driver, known as cng.sys, and could allow an attacker to escalate the privileges they have when accessing a Windows machine. The full technical detail can be found within the Google Project Zero disclosure, but slightly more simply put, it’s a memory buffer-overflow problem that could give an attacker admin-level control of the targeted Windows computer.
While attackers are known to be actively targeting Windows systems right now, that doesn’t mean your system is going down. Firstly, I should point out that, according to a confirmation from Shane Huntley, director of Google’s Threat Analysis Group, the attackers spotted exploiting the vulnerability are not targeting any U.S. election-related systems at this point. That’s good news, and there’s more.
While Microsoft has confirmed that the reported attack is real, it also suggests that it is limited in scope being targeted in nature. This is not, at least as of yet, a widespread broad-sweep exploit. Microsoft says that it has no evidence of any indication of widespread exploits.
Then there’s the attack itself which requires two vulnerabilities to be chained together for a successful exploit to happen. One of them has already been patched. That was a browser-based vulnerability, CVE-2020-15999, in Chrome browsers, including Microsoft Edge. As long as your browser is up to date, you are protected. Microsoft Edge was updated on October 22 while Google Chrome was updated on October 20.
There are no known other attack chains for the Windows vulnerability at this point. Which doesn’t mean your machine is 100% safe, as an attacker with access to an already compromised system could still exploit it. However, it does mean there’s no need to hit the panic button, truth be told. Microsoft has also confirmed that the vulnerability cannot be exploited to affect cryptographic functionality.
I reached out to Microsoft, and a spokesperson told me that “Microsoft has a customer commitment to investigate reported security issues and update impacted devices to protect customers.”
As for that seven-day disclosure deadline from the Google Project Zero team, the Microsoft spokesperson said that “while we work to meet all researchers’ deadlines for disclosures, including short-term deadlines like in this scenario, developing a security update is a balance between timeliness and quality, and our ultimate goal is to help ensure maximum customer protection with minimal customer disruption.”
Although Microsoft has not commented on the likely timing of a security patch to prevent exploitation of this Windows vulnerability, the Project Zero technical lead, Ben Hawkes, has tweeted that it is expected as part of the Patch Tuesday updates on November 10.
How big a threat is this to your average Windows user? That remains to be seen, but currently I’d classify it as a be aware but don’t panic situation. Hang-fire, ensure your web browsers are bang up to date, and you should be fine. There are far more significant risks to your data than this zero-day attack, in my never humble opinion. Risks such as phishing in all forms, password reuse, lack of two-factor authentication and software that isn’t kept up to date with security patches.