Ueberauth Guardian up to 2.4.0 Plug Keys keys.ex String.to_atom key allocation of resources

Summaryinfo

A vulnerability classified as problematic was found in Ueberauth Guardian up to 2.4.0. Affected by this vulnerability is the function String.to_atom of the file lib/guardian/plug/keys.ex of the component Plug Keys. The manipulation of the argument key results in allocation of resources. This vulnerability was named CVE-2026-54894. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability classified as problematic has been found in Ueberauth Guardian up to 2.4.0. Affected is the function String.to_atom of the file lib/guardian/plug/keys.ex of the component Plug Keys. The manipulation of the argument key with an unknown input leads to a allocation of resources vulnerability. CWE is classifying the issue as CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. This is going to have an impact on availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-54894 since 06/16/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1499.

Upgrading to version 2.4.1 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-51915). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• Ueberauth

Name

• Guardian

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4.0

Website

• Product: https://github.com/ueberauth/guardian/

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Once again VulDB remains the best source for vulnerability data.

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