Both Google and Mandiant are reporting a significant increase in the number of zero-day vulnerabilities reported in 2021.

Google:

2021 included the detection and disclosure of 58 in-the-wild 0-days, the most ever recorded since Project Zero began tracking in mid-2014. That’s more than double the previous maximum of 28 detected in 2015 and especially stark when you consider that there were only 25 detected in 2020. We’ve tracked publicly known in-the-wild 0-day exploits in this spreadsheet since mid-2014.

While we often talk about the number of 0-day exploits used in-the-wild, what we’re actually discussing is the number of 0-day exploits detected and disclosed as in-the-wild. And that leads into our first conclusion: we believe the large uptick in in-the-wild 0-days in 2021 is due to increased detection and disclosure of these 0-days, rather than simply increased usage of 0-day exploits.

Mandiant:

In 2021, Mandiant Threat Intelligence identified 80 zero-days exploited in the wild, which is more than double the previous record volume in 2019. State-sponsored groups continue to be the primary actors exploiting zero-day vulnerabilities, led by Chinese groups. The proportion of financially motivated actors­ — particularly ransomware groups — ­deploying zero-day exploits also grew significantly, and nearly 1 in 3 identified actors exploiting zero-days in 2021 was financially motivated. Threat actors exploited zero-days in Microsoft, Apple, and Google products most frequently, likely reflecting the popularity of these vendors. The vast increase in zero-day exploitation in 2021, as well as the diversification of actors using them, expands the risk portfolio for organizations in nearly every industry sector and geography, particularly those that rely on these popular systems.

News article.