Denial of Service via missing host header in specific logging configurations

Summary

Envoy is an open source edge and service proxy designed for cloud-native applications. From 1.37.0 until 1.37.5 and 1.38.3, when the %REQUESTED_SERVER_NAME(X:Y)% is used in log format and host related options is specified, like HOST_FIRST, SNI_FIRST, it's possible to crash Envoy when the specified host header is missing in the request headers. This vulnerability is fixed in 1.37.5 and 1.38.3. A flaw was found in Envoy. A remote attacker can exploit this vulnerability by sending a request with a missing host header when the `%REQUESTED_SERVER_NAME(X:Y)%` is used in the log format and host-related options, such as HOST_FIRST or SNI_FIRST, are specified. This can lead to a crash of the Envoy proxy, resulting in a Denial of Service (DoS). Red Hat products ship Envoy versions prior to 1.37.0, which do not contain the vulnerable %REQUESTED_SERVER_NAME% host-related logging code introduced in 1.37.0. Red Hat products are therefore not affected by this vulnerability. Red Hat severity: Important — CVSS 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H). Weakness: CWE-476. No fixing RHSA erratum has published yet; monitor the Red Hat CVE page and patch when it ships.