The ZlibDecoders in Netty 4.1.x before 4.1.46 allow for unbounded memory allocation while decoding a ZlibEncoded byte stream. An attacker could send a large ZlibEncoded byte stream to the Netty server, forcing the server to allocate all of its free memory to a single decoder.
https://www.oracle.com/security-alerts/cpujan2021.html
https://www.oracle.com/security-alerts/cpuapr2022.html
https://www.oracle.com/security-alerts/cpuApr2021.html
https://www.oracle.com//security-alerts/cpujul2021.html
https://www.debian.org/security/2021/dsa-4885
https://security.netapp.com/advisory/ntap-20201223-0001/
https://lists.debian.org/debian-lts-announce/2020/09/msg00003.html
https://github.com/netty/netty/pull/9924
https://github.com/netty/netty/issues/6168
https://github.com/netty/netty/compare/netty-4.1.45.Final...netty-4.1.46.Final