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CVE PROGRAM SOURCE RECORD8.7 High

CVE-2026-70399

httpd does not enforce the documented default max_clients connection limit

Read JSON ↗CVE.org ↗
Status
Published
Published
Updated
Assigning organization
EEF

Description

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. This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Erlang OTP

Default version status: unaffected

  • 17.0 to < 27.3.4.17affected
  • 28.0 to < 28.5.0.6affected
  • 29.0 to < 29.0.6affected
pkg:software-id/erlang.org/otp

Erlang OTP

Default version status: unaffected

  • 5.10 to < 9.3.2.7affected
  • 9.4 to < 9.6.2.3affected
  • 9.7 to < 9.7.2affected
pkg:otp/inets

Erlang OTP

Default version status: unaffected

  • d9674f32811cd5bb02b0d6656053b5ee226bc74c to < *affected
pkg:github/erlang/otp

References