buildkit/ExposeInvalidFormat

EXPOSE instruction should not define an IP address or host-port mapping.

Property	Value
Severity	Warning
Category	Correctness
Default	Enabled

Description

The EXPOSE instruction in a Dockerfile is used to indicate which ports the container listens on at runtime. It should not include an IP address or host-port mapping. Including an IP address or host-port mapping in the EXPOSE instruction does not actually publish the port and can be misleading. Use docker run -p or docker compose port mappings to bind host ports at runtime.

Examples

Bad:

FROM alpine
EXPOSE 127.0.0.1:80:80

Good:

FROM alpine
EXPOSE 80

Bad:

FROM alpine
EXPOSE 80:80

Good:

FROM alpine
EXPOSE 80

Reference