If the data size exceeds content-length, the remaining bytes on the wire are considered part of the response to the next (pipelined) request.
If there isn't an outstanding request to match with that response, see https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-p1-messaging-26#section-3.3.3 -
If the final response to the last request on a connection has been
completely received and there remains additional data to read, a user
agent MAY discard the remaining data or attempt to determine if that
data belongs as part of the prior response body, which might be the
case if the prior message's Content-Length value is incorrect. A
client MUST NOT process, cache, or forward such extra data as a
separate response, since such behavior would be vulnerable to cache
poisoning.