{"id":"CVE-2026-55734","summary":"guardian atom exhaustion in Guardian.Permissions.encode_permissions!/1","details":"Allocation of Resources Without Limits or Throttling vulnerability in ueberauth guardian (Guardian.Permissions module) allows a denial of service via BEAM atom-table exhaustion.\n\nThis 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.\n\nThe 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.\n\nThis issue affects guardian: from 2.0.0 before 2.4.1.","aliases":["EEF-CVE-2026-55734","GHSA-9qx2-v587-q3gg"],"modified":"2026-08-04T11:51:10.856721322Z","published":"2026-08-01T18:46:24.291Z","database_specific":{"unresolved_ranges":[{"extracted_events":[{"introduced":"b7a6128ca4d0ffb7f7df5219dd982304ff9d6802"},{"fixed":"8d4efbfc352d30f5fcfc75a4d69a795b0e472724"}],"source":"AFFECTED_FIELD"}],"cna_assigner":"EEF","cwe_ids":["CWE-770"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55734.json"},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-55734.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-55734"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55734.json"},{"type":"ADVISORY","url":"https://github.com/ueberauth/guardian/security/advisories/GHSA-9qx2-v587-q3gg"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55734"},{"type":"FIX","url":"https://github.com/ueberauth/guardian/commit/8d4efbfc352d30f5fcfc75a4d69a795b0e472724"},{"type":"PACKAGE","url":"https://github.com/ueberauth/guardian"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/ueberauth/guardian","events":[{"introduced":"576997d3701306ccfa40b42e18b1bec5a6ac98a7"},{"fixed":"e6017b492b8ef55e24fd08dea45ce11780d7b4f7"}],"database_specific":{"extracted_events":[{"introduced":"2.0.0"},{"fixed":"2.4.1"}],"source":"AFFECTED_FIELD"}}],"versions":["v2.4.0","v2.3.2","v2.3.1","v2.3.0","v2.2.4","v2.2.3","v2.2.2","v2.2.1","v2.1.2","v2.1.1","2.1.0","v2.0.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55734.json"}}],"schema_version":"1.8.0","severity":[{"type":"CVSS_V4","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"}]}