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.
CVSS
No CVSS.
References
Configurations
No configuration.
History
27 Apr 2026, 14:16
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2026-04-27 14:16
Updated : 2026-04-27 18:57
NVD link : CVE-2026-32688
Mitre link : CVE-2026-32688
CVE.ORG link : CVE-2026-32688
JSON object : View
Products Affected
No product.
CWE
CWE-770
Allocation of Resources Without Limits or Throttling