Envoy is a cloud-native, open source edge and service proxy. Due to how Envoy invoked the nlohmann JSON library, the library could throw an uncaught exception from downstream data if incomplete UTF-8 strings were serialized. The uncaught exception would cause Envoy to crash.
https://github.com/envoyproxy/envoy/security/advisories/GHSA-g979-ph9j-5gg4