{"affected":[{"package":{"ecosystem":"Hex","name":"plug_cowboy","purl":"pkg:hex/plug_cowboy"},"ranges":[{"events":[{"introduced":"2.0.0"},{"fixed":"2.8.1"}],"type":"SEMVER"}],"versions":["2.0.0","2.0.1","2.0.2","2.1.0","2.1.1","2.1.2","2.1.3","2.2.0","2.2.1","2.2.2","2.3.0","2.4.0","2.4.1","2.5.0","2.5.1","2.5.2","2.6.0","2.6.1","2.6.2","2.7.0","2.7.1","2.7.2","2.7.3","2.7.4","2.7.5","2.8.0"]},{"ranges":[{"events":[{"introduced":"12ecfd024bb179d48b018fecf074e43fe6a19c83"},{"fixed":"bfb34cb45eb354e56437f7023fb306de1bf9c19b"}],"repo":"https://github.com/elixir-plug/plug_cowboy","type":"GIT"}]}],"aliases":["GHSA-q8x4-x7mp-5vg2","CVE-2026-32688"],"credits":[{"name":"Peter Ullrich","type":"FINDER"}],"database_specific":{"capec_ids":["CAPEC-125"],"cpe_ids":["cpe:2.3:a:elixir-plug:plug_cowboy:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-770"]},"details":"## Summary\n\nAllocation of Resources Without Limits or Throttling vulnerability in elixir-plug plug_cowboy allows unauthenticated remote denial of service via atom table exhaustion.\n\nPlug.Cowboy.Conn.conn/1 in lib/plug/cowboy/conn.ex calls String.to_atom/1 on the value returned by :cowboy_req.scheme/1. For HTTP/2 connections, cowlib passes the client-supplied :scheme pseudo-header value through verbatim without validation. Each unique value permanently allocates a new entry in the BEAM atom table. Since atoms are never garbage-collected and the atom table has a fixed limit (default 1,048,576), an unauthenticated attacker can exhaust the table by sending HTTP/2 requests with unique :scheme values, causing the Erlang VM to abort with system_limit and taking down the entire node.\n\nThis vulnerability does not affect HTTP/1.1, where cowboy derives the scheme from the listener type rather than from a client-supplied header.\n\nThis issue affects plug_cowboy: from 2.0.0 before 2.8.1.\n\n## Workaround\n\nDisable HTTP/2 on the Plug.Cowboy.https/3 listener by passing protocol_options: %{protocols: [:http]} in the cowboy options. This restricts the listener to HTTP/1.1, where the scheme is derived from the listener type and is not attacker-controlled.","id":"EEF-CVE-2026-32688","modified":"2026-04-27T14:55:05.241Z","published":"2026-04-27T13:45:35.160Z","references":[{"type":"ADVISORY","url":"https://github.com/elixir-plug/plug_cowboy/security/advisories/GHSA-q8x4-x7mp-5vg2"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-32688.html"},{"type":"FIX","url":"https://github.com/elixir-plug/plug_cowboy/commit/bfb34cb45eb354e56437f7023fb306de1bf9c19b"},{"type":"PACKAGE","url":"https://hex.pm/packages/plug_cowboy"}],"related":[],"schema_version":"1.7.3","severity":[{"score":"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","type":"CVSS_V4"}],"summary":"Atom table exhaustion via HTTP/2 :scheme pseudo-header in plug_cowboy","upstream":[]}