{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "2.0.0"
              },
              {
                "fixed": "2.4.1"
              }
            ],
            "source": "AFFECTED_FIELD"
          },
          "events": [
            {
              "introduced": "576997d3701306ccfa40b42e18b1bec5a6ac98a7"
            },
            {
              "fixed": "e6017b492b8ef55e24fd08dea45ce11780d7b4f7"
            }
          ],
          "repo": "https://github.com/ueberauth/guardian",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-fjr5-7xrc-hmpj"
  ],
  "database_specific": {
    "cna_assigner": "EEF",
    "cwe_ids": [
      "CWE-770"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55733.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "b7a6128ca4d0ffb7f7df5219dd982304ff9d6802"
          },
          {
            "fixed": "9cd268557846aa4c3ad53566c08f2c190ee5513f"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unbounded atom creation from attacker-controlled binary input.\n\nGuardian.Permissions.AtomEncoding encodes permission scopes by passing arbitrary binaries to String.to_atom/1. When encode/3 in lib/guardian/permissions/atom_encoding.ex is called with a list, each binary entry is handled by the encode_value/3 binary clause, which calls String.to_atom(value) with no allow-list check. The perm_set argument (the application's small, finite set of legitimate permission names) is discarded, so any external string flows straight into atom creation. This encoder is selected with use Guardian.Permissions, encoding: Guardian.Permissions.AtomEncoding and reached through the imported encode/3 entry point.\n\nString.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 funnels attacker-influenced permission scopes (from a request body, a JWT claim, or other external input) into encode/3 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 with system_limit, taking down every application running on it.\n\nThe default encoder is Guardian.Permissions.BitwiseEncoding, which is not affected.\n\nThis issue affects guardian: from 2.0.0 before 2.4.1.",
  "id": "CVE-2026-55733",
  "modified": "2026-08-04T11:30:55.253349264Z",
  "published": "2026-08-01T18:46:12.113Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-55733.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-55733"
    },
    {
      "type": "WEB",
      "url": "https://repo.hex.pm"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55733.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/ueberauth/guardian/security/advisories/GHSA-fjr5-7xrc-hmpj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55733"
    },
    {
      "type": "FIX",
      "url": "https://github.com/ueberauth/guardian/commit/9cd268557846aa4c3ad53566c08f2c190ee5513f"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ueberauth/guardian"
    }
  ],
  "schema_version": "1.8.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Atom-table exhaustion denial of service in Guardian permissions AtomEncoding via unbounded atom creation"
}