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VulnerabilityPublished Updated

CVE-2026-32688: elixir-plug plug_cowboy · Unthrottled Resource Allocation

Affects elixir-plug plug_cowboySource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 2.8.1 soon.

Data as of 30 Oct 2026, 06:59 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 45% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.8.1, bfb34cb45eb354e56437f7023fb306de1bf9c19b
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 27 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade plug_cowboy to 2.8.1; plug_cowboy to bfb34cb45eb354e56437f7023fb306de1bf9c19b.

Affected software

ProductAffectedFixed in
elixir-plugplug_cowboyAffected
  • >=2.0.0 <2.8.1
Fixed in
  • 2.8.1
elixir-plugplug_cowboyAffected
  • ≥ 12ecfd024bb179d48b018fecf074e43fe6a19c83, < bfb34cb45eb354e56437f7023fb306de1bf9c19b
Fixed in
  • bfb34cb45eb354e56437f7023fb306de1bf9c19b
Hexplug_cowboypkg:hex/plug_cowboyOther threatsAffected
  • >=2.0.0 <2.8.1
Fixed in
  • 2.8.1

CPE configurations (1)

  • cpe:2.3:a:elixir-plug:plug_cowboy:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, consider mitigating by disabling or restricting HTTP/2 support in plug_cowboy if feasible, or applying network-level controls to limit or validate incoming HTTP/2 :scheme headers. Avoid relying on HTTP/2 connections from untrusted sources.

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.

References

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