{"id":"CVE-2026-32688","aliases":["EEF-CVE-2026-32688","GHSA-q8x4-x7mp-5vg2"],"url":"https://o3.security/vulnerability/CVE-2026-32688","summary":"Atom table exhaustion via HTTP/2 :scheme pseudo-header in plug_cowboy","details":"Allocation 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.","published":"2026-04-27T13:45:35.160Z","modified":"2026-07-15T01:48:59.058522871Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Hex","name":"plug_cowboy","fixedVersion":"2.8.1"}],"fix":{"url":"https://github.com/elixir-plug/plug_cowboy/commit/bfb34cb45eb354e56437f7023fb306de1bf9c19b","label":"elixir-plug/plug_cowboy@bfb34cb"},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-32688.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-32688"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/32xxx/CVE-2026-32688.json"},{"type":"ADVISORY","url":"https://github.com/elixir-plug/plug_cowboy/security/advisories/GHSA-q8x4-x7mp-5vg2"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-32688"},{"type":"FIX","url":"https://github.com/elixir-plug/plug_cowboy/commit/bfb34cb45eb354e56437f7023fb306de1bf9c19b"},{"type":"PACKAGE","url":"https://github.com/elixir-plug/plug_cowboy"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-15T01:48:59.058522871Z"}}