Description
Allocation of Resources Without Limits or Throttling vulnerability in elixir-plug plug_cowboy allows unauthenticated remote denial of service via atom table exhaustion.
Plug.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.
This vulnerability does not affect HTTP/1.1, where cowboy derives the scheme from the listener type rather than from a client-supplied header.
This issue affects plug_cowboy: from 2.0.0 before 2.8.1.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| elixir-plug | plug_cowboy | 2.0.0 – < 2.8.1 | 2.8.1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Hex | plug_cowboy | >= 2.0.0, < 2.8.1 | 2.8.1 | EEF-CVE-2026-32688 |
References
- https://github.com/elixir-plug/plug_cowboy/security/advisories/GHSA-q8x4-x7mp-5vg2 vendor-advisory related
- https://cna.erlef.org/cves/CVE-2026-32688.html related
- https://osv.dev/vulnerability/EEF-CVE-2026-32688 related
- https://github.com/elixir-plug/plug_cowboy/commit/bfb34cb45eb354e56437f7023fb306de1bf9c19b patch