This vulnerability is only exploitable in applications that use Guardian.Permissions (via use Guardian.Permissions) and route attacker-influenced data into encode_permissions!/1 or encode_permissions_into_claims!/2, for example by reading a permissions map from a request body and passing it into token issuance.
"}],"value":"This vulnerability is only exploitable in applications that use Guardian.Permissions (via use Guardian.Permissions) and route attacker-influenced data into encode_permissions!/1 or encode_permissions_into_claims!/2, for example by reading a permissions map from a request body and passing it into token issuance."}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*","versionEndExcluding":"2.4.1","versionStartIncluding":"2.0.0","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"AND"}],"credits":[{"lang":"en","type":"finder","value":"Peter Ullrich"},{"lang":"en","type":"remediation developer","value":"Yordis Prieto"},{"lang":"en","type":"analyst","value":"Jonatan Männchen / EEF"}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"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.
"}],"value":"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."}],"impacts":[{"capecId":"CAPEC-130","descriptions":[{"lang":"en","value":"CAPEC-130 Excessive Allocation"}]}],"metrics":[{"cvssV4_0":{"attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"LOCAL","baseScore":6.9,"baseSeverity":"MEDIUM","privilegesRequired":"NONE","subAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-770","description":"CWE-770 Allocation of Resources Without Limits or Throttling","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-08-01T18:46:24.291Z","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","shortName":"EEF"},"references":[{"tags":["vendor-advisory","related"],"url":"https://github.com/ueberauth/guardian/security/advisories/GHSA-9qx2-v587-q3gg"},{"tags":["related"],"url":"https://cna.erlef.org/cves/CVE-2026-55734.html"},{"tags":["related"],"url":"https://osv.dev/vulnerability/EEF-CVE-2026-55734"},{"tags":["patch"],"url":"https://github.com/ueberauth/guardian/commit/8d4efbfc352d30f5fcfc75a4d69a795b0e472724"}],"source":{"discovery":"EXTERNAL"},"title":"guardian atom exhaustion in Guardian.Permissions.encode_permissions!/1","workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Before calling encode_permissions!/1 or encode_permissions_into_claims!/2, filter the permission map so that only keys belonging to the configured permission set are passed in, discarding any unknown keys. Avoid passing attacker-influenced permission maps into these functions.
"}],"value":"Before calling encode_permissions!/1 or encode_permissions_into_claims!/2, filter the permission map so that only keys belonging to the configured permission set are passed in, discarding any unknown keys. Avoid passing attacker-influenced permission maps into these functions."}],"x_generator":{"engine":"cvelib 1.8.0"}}},"cveMetadata":{"assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","assignerShortName":"EEF","cveId":"CVE-2026-55734","datePublished":"2026-08-01T18:46:24.291Z","dateReserved":"2026-06-17T10:44:34.365Z","dateUpdated":"2026-08-01T18:46:24.291Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"}