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": { "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-08-01T18:46:24.291Z" }, "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" } }, "adp": [ { "references": [ { "url": "https://github.com/ueberauth/guardian/security/advisories/GHSA-9qx2-v587-q3gg", "tags": [ "exploit" ] } ], "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2026-08-03T16:49:36.457207Z", "id": "CVE-2026-55734", "options": [ { "Exploitation": "poc" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-08-03T16:49:59.913Z" } } ] } }