{"id":"CVE-2026-55734","aliases":["EEF-CVE-2026-55734","GHSA-9qx2-v587-q3gg"],"url":"https://o3.security/vulnerability/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.","published":"2026-08-01T18:46:24.291Z","modified":"2026-08-12T03:51:41.043088440Z","cvss":null,"epss":{"score":0.00286,"percentile":0.21116,"asOf":"2026-08-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[],"fix":{"url":"https://github.com/ueberauth/guardian/commit/8d4efbfc352d30f5fcfc75a4d69a795b0e472724","label":"ueberauth/guardian@8d4efbf"},"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:41.043088440Z"}}