# CVE-2026-32688

> Vulnerability.

## 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.

## Key facts

- **CVE ID:** CVE-2026-32688
- **Published:** 2026-04-27
- **CWE codes:** CWE-770

## Primary sources

- NIST NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-32688

## Citation

> AI Analytics. CVE-2026-32688. Retrieved 2026-07-24 from https://api.ai-analytics.org/cve/CVE-2026-32688. Derived from NIST NVD. Licensed CC0.

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