High [CVE-2026-70399] Denial of Service via unenforced connection limit

Allocation of Resources Without Limits or Throttling vulnerability in Erlang/OTP inets httpd allows an unauthenticated remote attacker to cause denial of service by opening and holding open a large number of connections.

The max_clients option is documented to default to 150, and the inets hardening guide presents that limit as the first layer of denial-of-service defence, but a server that does not set it explicitly accepts an unlimited number of simultaneous connections. Establishing the connections is sufficient; no valid request and no authentication are required.

The accept gate in httpd_manager:handle_new_connection/4 reads the option with httpd_util:lookup/2, which returns undefined when the key is absent, rather than the three-argument form carrying the 150 default that the neighbouring get_ustate/2 uses.

Erlang term ordering places every integer before every atom, so the Count =< Max guard holds for any connection count and the server never returns {reject, busy}. Each accepted connection occupies a worker process and a socket for as long as it is held, driving the node towards process, memory and file descriptor exhaustion.

Servers that set max_clients explicitly are unaffected, because a configured value is applied as intended.

Affected product named by the advisory: Red Hat Hardened Images.