VulnerabilityAnalyzed

CVE-2026-32688

Allocation of Resources Without Limits or Throttling vulnerability in elixir-plug plug_cowboy allows unauthenticated remote denial of service via atom table exhaustion.

HIGH 8.7EPSS 0.55%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.55%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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.

CVSS 4.0: 8.7 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.55% probability · 44th percentile
CISA KEV: Not listed
Weakness: CWE-770
Affected: elixir-plug/plug.cowboy
Source: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

References

https://cna.erlef.org/cves/CVE-2026-32688.htmlThird Party Advisory
https://github.com/elixir-plug/plug_cowboy/commit/bfb34cb45eb354e56437f7023fb306de1bf9c19bPatch
https://github.com/elixir-plug/plug_cowboy/security/advisories/GHSA-q8x4-x7mp-5vg2Vendor Advisory
https://osv.dev/vulnerability/EEF-CVE-2026-32688Third Party Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.