CVE-2026-70399 (GCVE-0-2026-70399)

Vulnerability from cvelistv5 – Published: 2026-09-01 14:33 – Updated: 2026-09-01 15:52
VLAI
Title
httpd does not enforce the documented default max_clients connection limit
Summary
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.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-01 15:52 UTC
CWE
  • CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
Impacted products
Vendor Product Version CPE status
Erlang OTP Affected: 17.0 , < 27.3.4.17 (otp)
Affected: 28.0 , < 28.5.0.6 (otp)
Affected: 29.0 , < 29.0.6 (otp)
    cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
Create a notification for this product.
Erlang OTP Affected: 5.10 , < 9.3.2.7 (otp)
Affected: 9.4 , < 9.6.2.3 (otp)
Affected: 9.7 , < 9.7.2 (otp)
    cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
Create a notification for this product.
Erlang OTP Affected: d9674f32811cd5bb02b0d6656053b5ee226bc74c , < * (git)
    cpe:2.3:a:erlang:erlang\/otp:*:*:*:*:*:*:*:*
Create a notification for this product.
Credits
Lukas Backström / Erlang Solutions Lukas Backström / Erlang Solutions Konrad Pietrzak / Ericsson
Show details on NVD website
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    "vulnrichment": {
      "containers": "{\"cna\": {\"affected\": [{\"cpes\": [\"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\"], \"defaultStatus\": \"unaffected\", \"modules\": [\"httpd_manager\"], \"packageName\": \"otp\", \"packageURL\": \"pkg:sid/erlang.org/otp\", \"product\": \"OTP\", \"programFiles\": [\"lib/inets/src/http_server/httpd_manager.erl\"], \"programRoutines\": [{\"name\": \"httpd_manager:handle_new_connection/4\"}, {\"name\": \"httpd_manager:new_connection/1\"}], \"vendor\": \"Erlang\", \"versions\": [{\"lessThan\": \"27.3.4.17\", \"status\": \"affected\", \"version\": \"17.0\", \"versionType\": \"otp\"}, {\"lessThan\": \"28.5.0.6\", \"status\": \"affected\", \"version\": \"28.0\", \"versionType\": \"otp\"}, {\"lessThan\": \"29.0.6\", \"status\": \"affected\", \"version\": \"29.0\", \"versionType\": \"otp\"}]}, {\"cpes\": [\"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\"], \"defaultStatus\": \"unaffected\", \"modules\": [\"httpd_manager\"], \"packageName\": \"inets\", \"packageURL\": \"pkg:otp/inets\", \"product\": \"OTP\", \"programFiles\": [\"src/http_server/httpd_manager.erl\"], \"programRoutines\": [{\"name\": \"httpd_manager:handle_new_connection/4\"}, {\"name\": \"httpd_manager:new_connection/1\"}], \"repo\": \"https://github.com/erlang/otp\", \"vendor\": \"Erlang\", \"versions\": [{\"lessThan\": \"9.3.2.7\", \"status\": \"affected\", \"version\": \"5.10\", \"versionType\": \"otp\"}, {\"lessThan\": \"9.6.2.3\", \"status\": \"affected\", \"version\": \"9.4\", \"versionType\": \"otp\"}, {\"lessThan\": \"9.7.2\", \"status\": \"affected\", \"version\": \"9.7\", \"versionType\": \"otp\"}]}, {\"collectionURL\": \"https://github.com\", \"cpes\": [\"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\"], \"defaultStatus\": \"unaffected\", \"modules\": [\"httpd_manager\"], \"packageName\": \"erlang/otp\", \"packageURL\": \"pkg:github/erlang/otp\", \"product\": \"OTP\", \"programFiles\": [\"lib/inets/src/http_server/httpd_manager.erl\"], \"programRoutines\": [{\"name\": \"httpd_manager:handle_new_connection/4\"}, {\"name\": \"httpd_manager:new_connection/1\"}], \"repo\": \"https://github.com/erlang/otp\", \"vendor\": \"Erlang\", \"versions\": [{\"changes\": [{\"at\": \"d94a94c96eb4cccbd6f7d7da5975f0c035b69612\", \"status\": \"unaffected\"}, {\"at\": \"6746dc4e1df5257ad8ac91cbbd167cb8b0274ce7\", \"status\": \"unaffected\"}, {\"at\": \"e0050fc00c500a4fa9ba1f594603c787ff6d20b2\", \"status\": \"unaffected\"}], \"lessThan\": \"*\", \"status\": \"affected\", \"version\": \"d9674f32811cd5bb02b0d6656053b5ee226bc74c\", \"versionType\": \"git\"}]}], \"configurations\": [{\"lang\": \"en\", \"supportingMedia\": [{\"base64\": false, \"type\": \"text/html\", \"value\": \"\u003cp\u003eOnly servers that do not set \u003ccode\u003emax_clients\u003c/code\u003e in the httpd configuration are affected. A server that sets the option to any integer value applies the limit as intended.\u003c/p\u003e\"}, {\"base64\": false, \"type\": \"text/markdown\", \"value\": \"Only servers that do not set `max_clients` in the httpd configuration are affected. A server that sets the option to any integer value applies the limit as intended.\"}], \"value\": \"Only servers that do not set max_clients in the httpd configuration are affected. A server that sets the option to any integer value applies the limit as intended.\"}], \"cpeApplicability\": [{\"nodes\": [{\"cpeMatch\": [{\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"versionEndExcluding\": \"27.3.4.17\", \"versionStartIncluding\": \"17.0\", \"vulnerable\": true}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"versionEndExcluding\": \"28.5.0.6\", \"versionStartIncluding\": \"28.0\", \"vulnerable\": true}, {\"criteria\": \"cpe:2.3:a:erlang:erlang\\\\/otp:*:*:*:*:*:*:*:*\", \"versionEndExcluding\": \"29.0.6\", \"versionStartIncluding\": \"29.0\", \"vulnerable\": true}], \"negate\": false, \"operator\": \"OR\"}], \"operator\": \"AND\"}], \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"Lukas Backstr\\u00f6m / Erlang Solutions\"}, {\"lang\": \"en\", \"type\": \"remediation developer\", \"value\": \"Lukas Backstr\\u00f6m / Erlang Solutions\"}, {\"lang\": \"en\", \"type\": \"remediation reviewer\", \"value\": \"Konrad Pietrzak / Ericsson\"}], \"descriptions\": [{\"lang\": \"en\", \"supportingMedia\": [{\"base64\": false, \"type\": \"text/html\", \"value\": \"\u003cp\u003eAllocation 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 \u003ccode\u003emax_clients\u003c/code\u003e option is documented to default to \u003ccode\u003e150\u003c/code\u003e, 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.\u003c/p\u003e\\n\u003cp\u003eThe accept gate in \u003ccode\u003ehttpd_manager:handle_new_connection/4\u003c/code\u003e reads the option with \u003ccode\u003ehttpd_util:lookup/2\u003c/code\u003e, which returns \u003ccode\u003eundefined\u003c/code\u003e when the key is absent, rather than the three-argument form carrying the \u003ccode\u003e150\u003c/code\u003e default that the neighbouring \u003ccode\u003eget_ustate/2\u003c/code\u003e uses. Erlang term ordering places every integer before every atom, so the \u003ccode\u003eCount =\u0026lt; Max\u003c/code\u003e guard holds for any connection count and the server never returns \u003ccode\u003e{reject, busy}\u003c/code\u003e. 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 \u003ccode\u003emax_clients\u003c/code\u003e explicitly are unaffected, because a configured value is applied as intended.\u003c/p\u003e\\n\u003cp\u003eThis issue affects OTP from OTP\u0026nbsp;17.0 before OTP\u0026nbsp;27.3.4.17, from OTP\u0026nbsp;28.0 before OTP\u0026nbsp;28.5.0.6, and from OTP\u0026nbsp;29.0 before OTP\u0026nbsp;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.\u003c/p\u003e\"}, {\"base64\": false, \"type\": \"text/markdown\", \"value\": \"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.\\n\\nThe 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 =\u003c 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.\\n\\nThis issue affects OTP from OTP\\u00a017.0 before OTP\\u00a027.3.4.17, from OTP\\u00a028.0 before OTP\\u00a028.5.0.6, and from OTP\\u00a029.0 before OTP\\u00a029.0.6, 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.\"}], \"value\": \"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. 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Servers that set max_clients explicitly are unaffected, because a configured value is applied as intended.\\n\\nThis issue affects OTP from OTP\\u00a017.0 before OTP\\u00a027.3.4.17, from OTP\\u00a028.0 before OTP\\u00a028.5.0.6, and from OTP\\u00a029.0 before OTP\\u00a029.0.6, 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.\"}], \"impacts\": [{\"capecId\": \"CAPEC-469\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"CAPEC-469 HTTP DoS\"}]}], \"metrics\": [{\"cvssV4_0\": {\"Automatable\": \"NOT_DEFINED\", \"Recovery\": \"NOT_DEFINED\", \"Safety\": \"NOT_DEFINED\", \"attackComplexity\": \"LOW\", \"attackRequirements\": \"NONE\", \"attackVector\": \"NETWORK\", \"baseScore\": 8.7, \"baseSeverity\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"providerUrgency\": \"NOT_DEFINED\", \"subAvailabilityImpact\": \"NONE\", \"subConfidentialityImpact\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N\", \"version\": \"4.0\", \"vulnAvailabilityImpact\": \"HIGH\", \"vulnConfidentialityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"NONE\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"format\": \"CVSS\", \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"problemTypes\": [{\"descriptions\": [{\"cweId\": \"CWE-770\", \"description\": \"CWE-770 Allocation of Resources Without Limits or Throttling\", \"lang\": \"en\", \"type\": \"CWE\"}]}], \"providerMetadata\": {\"orgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"shortName\": \"EEF\", \"dateUpdated\": \"2026-09-01T14:33:05.717Z\"}, \"references\": [{\"tags\": [\"vendor-advisory\", \"related\"], \"url\": \"https://github.com/erlang/otp/security/advisories/GHSA-pwvh-c689-f8q5\"}, {\"tags\": [\"related\"], \"url\": \"https://cna.erlef.org/cves/CVE-2026-70399.html\"}, {\"tags\": [\"related\"], \"url\": \"https://osv.dev/vulnerability/EEF-CVE-2026-70399\"}, {\"tags\": [\"x_version-scheme\"], \"url\": \"https://www.erlang.org/doc/system/versions.html#order-of-versions\"}, {\"tags\": [\"patch\"], \"url\": \"https://github.com/erlang/otp/commit/d94a94c96eb4cccbd6f7d7da5975f0c035b69612\"}, {\"tags\": [\"patch\"], \"url\": \"https://github.com/erlang/otp/commit/6746dc4e1df5257ad8ac91cbbd167cb8b0274ce7\"}, {\"tags\": [\"patch\"], \"url\": \"https://github.com/erlang/otp/commit/e0050fc00c500a4fa9ba1f594603c787ff6d20b2\"}], \"source\": {\"discovery\": \"EXTERNAL\"}, \"title\": \"httpd does not enforce the documented default max_clients connection limit\", \"workarounds\": [{\"lang\": \"en\", \"supportingMedia\": [{\"base64\": false, \"type\": \"text/html\", \"value\": \"\u003cul\u003e\\n\u003cli\u003eSet \u003ccode\u003emax_clients\u003c/code\u003e explicitly in the httpd configuration, for example \u003ccode\u003e{max_clients, 150}\u003c/code\u003e. 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An explicitly configured value is read by the same accept gate and applied as intended, so this restores the documented limit without upgrading.\\n* Limit concurrent connections in front of httpd, for example with reverse proxy or firewall connection-count and connection-rate rules.\\n* Restrict access to the server to trusted clients where the deployment allows it.\"}], \"value\": \"* Set max_clients explicitly in the httpd configuration, for example {max_clients, 150}. An explicitly configured value is read by the same accept gate and applied as intended, so this restores the documented limit without upgrading.\\n* Limit concurrent connections in front of httpd, for example with reverse proxy or firewall connection-count and connection-rate rules.\\n* Restrict access to the server to trusted clients where the deployment allows it.\"}]}, \"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-70399\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-09-01T15:52:45.671034Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-09-01T15:52:49.600Z\"}}]}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-70399\", \"assignerOrgId\": \"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\", \"state\": \"PUBLISHED\", \"assignerShortName\": \"EEF\", \"dateReserved\": \"2026-08-06T13:00:02.045Z\", \"datePublished\": \"2026-09-01T14:33:05.717Z\", \"dateUpdated\": \"2026-09-01T15:52:53.186Z\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.