Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unbounded atom creation from attacker-influenced binary input.

Guardian.Plug.Keys derives connection and session namespace keys by passing arbitrary binaries to String.to_atom/1. base_key/1 in lib/guardian/plug/keys.ex converts any binary into the atom :"guardian_<input>", and the derived helpers claims_key/1, resource_key/1, and token_key/1 create a second atom on top of that. key_from_other/1 likewise converts a regex-captured binary through String.to_atom/1. The public specs advertise String.t() as a valid argument, so passing a string is documented usage, and higher-level entry points such as Guardian.Plug.current_token(conn, key: key) thread the caller-supplied key straight into these functions.

String.to_atom/1 creates a brand-new atom for every previously unseen binary, atoms are never garbage collected, and the BEAM atom table is fixed at roughly 1,048,576 entries by default. An application that routes attacker-influenced data (a tenant identifier, header, or other request input) into a Guardian key therefore mints one permanent atom per distinct value. A modest stream of varied, unauthenticated input permanently consumes the atom table and crashes the BEAM node, taking down every application running on it.

This issue affects guardian: from 0.1.0 before 2.4.1.

AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CWE-770

https://cna.erlef.org/cves/CVE-2026-54894.html

https://github.com/ueberauth/guardian/commit/2952657e42e6341a67e6aaad09d8f0b40ae917cb

https://github.com/ueberauth/guardian/security/advisories/GHSA-xqch-c77q-rgh5

https://osv.dev/vulnerability/EEF-CVE-2026-54894

[{"vendor":"ueberauth","product":"guardian","defaultStatus":"unaffected","collectionURL":"https://repo.hex.pm","packageName":"guardian","cpes":["cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Guardian.Plug.Keys'"],"programFiles":["lib/guardian/plug/keys.ex"],"programRoutines":[{"name":"'Elixir.Guardian.Plug.Keys':base_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':claims_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':resource_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':token_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':key_from_other/1"}],"repo":"https://github.com/ueberauth/guardian","packageURL":"pkg:hex/guardian","versions":[{"version":"0.1.0","lessThan":"2.4.1","versionType":"semver","status":"affected"}]},{"vendor":"ueberauth","product":"guardian","defaultStatus":"unaffected","collectionURL":"https://github.com","packageName":"ueberauth/guardian","cpes":["cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Guardian.Plug.Keys'"],"programFiles":["lib/guardian/plug/keys.ex"],"programRoutines":[{"name":"'Elixir.Guardian.Plug.Keys':base_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':claims_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':resource_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':token_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':key_from_other/1"}],"repo":"https://github.com/ueberauth/guardian","packageURL":"pkg:github/ueberauth/guardian","versions":[{"version":"7126fa433afc2563fcac0c9aa35193965f8fd5f8","lessThan":"2952657e42e6341a67e6aaad09d8f0b40ae917cb","versionType":"git","status":"affected"}]}]