title: X.509 subjectAltName matching bypass in Envoy
description: Envoy is an open source edge and service proxy, designed for cloud-native applications. The default_validator.cc implementation used to implement the default certificate validation routines has a "type confusion" bug when processing subjectAltNames. This processing allows, for example, an rfc822Name or uniformResourceIndicator to be authenticated as a domain name. This confusion allows for the bypassing of nameConstraints, as processed by the underlying OpenSSL/BoringSSL implementation, exposing the possibility of impersonation of arbitrary servers. As a result Envoy will trust upstream certificates that should not be trusted.
problem types: CWE-295: Improper Certificate Validation
affected:
{
product: envoy
vendor: envoyproxy
versions:
status: affected, version: < 1.20.2
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: NONE
baseScore: 7.4
baseSeverity: HIGH
confidentialityImpact: HIGH
integrityImpact: HIGH
privilegesRequired: NONE
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
version: 3.1
]