A flaw was discovered in Netty, a Java NIO client/server socket framework. The HTTP/2 protocol implementation allowed a denial of service (server resource consumption) because request cancellation can reset many streams quickly. This problem is also known as Rapid Reset Attack.
For Debian 10 buster, this problem has been fixed in version 1:4.1.33-1+deb10u4.
We recommend that you upgrade your netty packages.
For the detailed security status of netty please refer to its security tracker page at: https://security-tracker.debian.org/tracker/netty
Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: https://wiki.debian.org/LTS