---
id: CVE-2026-55734
title: >-
  Allocation of Resources Without Limits or Throttling vulnerability in
  ueberauth guardian (Guardian.Permissions module) allows a denial of service
  via BEAM atom-table exhaustion.


  This vulnerability is associated with program file lib/gua…
summary: >-
  Allocation of Resources Without Limits or Throttling vulnerability in
  ueberauth guardian (Guardian.Permissions module) allows a denial of service
  via BEAM atom-table exhaustion.


  This vulnerability is associated with program file lib/gua…
severity: none
cwe:
  - CWE-770
published: '2026-08-01'
updated: '2026-08-01'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-55734'
references:
  - url: 'https://cna.erlef.org/cves/CVE-2026-55734.html'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/ueberauth/guardian/commit/8d4efbfc352d30f5fcfc75a4d69a795b0e472724
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: >-
      https://github.com/ueberauth/guardian/security/advisories/GHSA-9qx2-v587-q3gg
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
  - url: 'https://osv.dev/vulnerability/EEF-CVE-2026-55734'
    label: 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
tags:
  - nvd
ingestedAt: '2026-08-02T09:18:11.908Z'
epss: 0.00476
epssPercentile: 0.38458
---

## Overview

Allocation of Resources Without Limits or Throttling vulnerability in ueberauth guardian (Guardian.Permissions module) allows a denial of service via BEAM atom-table exhaustion.

This vulnerability is associated with program file lib/guardian/permissions.ex and program routines 'Elixir.Guardian.Permissions':encode_permissions!/1, 'Elixir.Guardian.Permissions':encode_permissions_into_claims!/2, 'Elixir.Guardian.Permissions':do_encode_permissions!/2.

The Guardian.Permissions mixin installs a public encode_permissions!/1 function on every module that does use Guardian.Permissions. For each key of the supplied map, encode_permissions!/1 calls String.to_atom(to_string(k)) before any validation runs. The integer-value clause of do_encode_permissions!/2 then short-circuits straight to encoding without validating the key against the configured permission set, so a key with an integer value is interned as a fresh atom with no exception raised. Atoms are never garbage collected and the BEAM atom table is a fixed-size resource (default roughly 1,048,576 entries), so each unique attacker-chosen key permanently consumes one slot. An attacker who can influence a permission map that reaches encode_permissions!/1 (for example a permissions map read from a request body and passed into token issuance via encode_permissions_into_claims!/2) can mint an unbounded number of atoms and exhaust the atom table, crashing the entire BEAM node and every service running on it. The sibling decode_permissions/1 is not affected because it skips keys absent from the configured permission set.

This issue affects guardian: from 2.0.0 before 2.4.1.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.