{"id":82618,"date":"2026-07-28T13:46:50","date_gmt":"2026-07-28T10:16:50","guid":{"rendered":"https:\/\/afaghhosting.net\/blog\/cve-2026-65624-cowboy-http-1-1-max_headers-bypass-via-duplicate-header-names-enables-memory-exhaustion\/"},"modified":"2026-07-28T13:46:50","modified_gmt":"2026-07-28T10:16:50","slug":"cve-2026-65624-cowboy-http-1-1-max_headers-bypass-via-duplicate-header-names-enables-memory-exhaustion","status":"publish","type":"post","link":"https:\/\/afaghhosting.net\/blog\/cve-2026-65624-cowboy-http-1-1-max_headers-bypass-via-duplicate-header-names-enables-memory-exhaustion\/","title":{"rendered":"CVE-2026-65624 &#8211; Cowboy HTTP\/1.1 max_headers Bypass via Duplicate Header Names Enables Memory Exhaustion"},"content":{"rendered":"<p>CVE ID :CVE-2026-65624<\/p>\n<p>  Published : July 28, 2026, 10:16 a.m. | 23\u00a0minutes ago<\/p>\n<p>  Description :Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowboy allows an unauthenticated remote attacker to exhaust connection process memory over HTTP\/1.1.<\/p>\n<p>The HTTP\/1.1 handler in cowboy_http enforces the max_headers limit by counting the number of distinct header names in a map (maps:size(Headers)). When a request contains multiple header lines with the same name, the values are concatenated into a single ever-growing binary stored under that one map key (&#8220;, &#8221; for regular headers, &#8220;; &#8221; for cookies), so the map size stays at one and the max_headers cap (default 100) is never reached. Because no accumulator bounds the total number of header lines or the total byte size of the header block (only per-line max_header_name_length and max_header_value_length apply), an unauthenticated client can send an arbitrary number of header lines with the same name and grow the connection process&#8217;s binary memory to arbitrary size within the request window.<\/p>\n<p>The impact per connection is bounded by request_timeout (default 5 seconds, not reset by header data), and by max_heap_size when set (the offending connection process is killed once its heap grows past the limit). When max_heap_size is left at the default (unset), sustained abuse can drive the Erlang VM into out-of-memory conditions.<\/p>\n<p>This issue affects cowboy from 2.0.0-pre.4 before 2.18.0.<\/p>\n<p>  Severity: 6.9 | MEDIUM<\/p>\n<p>  Visit the link for more details, such as CVSS details, affected products, timeline, and more&#8230;\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"<p>CVE ID :CVE-2026-65624 Published : July 28, 2026, 10:16 a.m. | 23\u00a0minutes ago Description :Allocation of Resources Without Limits or Throttling vulnerability in ninenines cowboy allows an unauthenticated remote attacker to exhaust connection process memory over HTTP\/1.1. The HTTP\/1.1 handler in cowboy_http enforces the max_headers limit by counting the number of distinct header names in &hellip;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[26],"tags":[],"class_list":["post-82618","post","type-post","status-publish","format-standard","hentry","category-vulnerability"],"_links":{"self":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/82618","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/comments?post=82618"}],"version-history":[{"count":0,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/posts\/82618\/revisions"}],"wp:attachment":[{"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/media?parent=82618"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/categories?post=82618"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/afaghhosting.net\/blog\/wp-json\/wp\/v2\/tags?post=82618"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}