{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-55733", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-06-17T10:44:34.365Z", "datePublished": "2026-08-01T18:46:12.113Z", "dateUpdated": "2026-08-01T18:46:12.113Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.Guardian.Permissions.AtomEncoding'"], "packageName": "guardian", "packageURL": "pkg:hex/guardian", "product": "guardian", "programFiles": ["lib/guardian/permissions/atom_encoding.ex"], "programRoutines": [{"name": "'Elixir.Guardian.Permissions.AtomEncoding':encode/3"}, {"name": "'Elixir.Guardian.Permissions.AtomEncoding':encode_value/3"}], "repo": "https://github.com/ueberauth/guardian", "vendor": "ueberauth", "versions": [{"lessThan": "2.4.1", "status": "affected", "version": "2.0.0", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.Guardian.Permissions.AtomEncoding'"], "packageName": "ueberauth/guardian", "packageURL": "pkg:github/ueberauth/guardian", "product": "guardian", "programFiles": ["lib/guardian/permissions/atom_encoding.ex"], "programRoutines": [{"name": "'Elixir.Guardian.Permissions.AtomEncoding':encode/3"}, {"name": "'Elixir.Guardian.Permissions.AtomEncoding':encode_value/3"}], "repo": "https://github.com/ueberauth/guardian", "vendor": "ueberauth", "versions": [{"lessThan": "9cd268557846aa4c3ad53566c08f2c190ee5513f", "status": "affected", "version": "b7a6128ca4d0ffb7f7df5219dd982304ff9d6802", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Only applications that opt into the non-default <tt>Guardian.Permissions.AtomEncoding</tt> encoder (via <tt>use Guardian.Permissions, encoding: Guardian.Permissions.AtomEncoding</tt>) and pass attacker-influenced permission scopes into its <tt>encode/3</tt> entry point are exploitable. The default <tt>Guardian.Permissions.BitwiseEncoding</tt> encoder and the <tt>Guardian.Permissions.TextEncoding</tt> encoder do not create atoms and are not affected.</p>"}], "value": "Only applications that opt into the non-default Guardian.Permissions.AtomEncoding encoder (via use Guardian.Permissions, encoding: Guardian.Permissions.AtomEncoding) and pass attacker-influenced permission scopes into its encode/3 entry point are exploitable. The default Guardian.Permissions.BitwiseEncoding encoder and the Guardian.Permissions.TextEncoding encoder do not create atoms and are not affected."}], "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 M\u00e4nnchen / EEF"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unbounded atom creation from attacker-controlled binary input.</p><p><tt>Guardian.Permissions.AtomEncoding</tt> encodes permission scopes by passing arbitrary binaries to <tt>String.to_atom/1</tt>. When <tt>encode/3</tt> in <tt>lib/guardian/permissions/atom_encoding.ex</tt> is called with a list, each binary entry is handled by the <tt>encode_value/3</tt> binary clause, which calls <tt>String.to_atom(value)</tt> with no allow-list check. The <tt>perm_set</tt> 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 <tt>use Guardian.Permissions, encoding: Guardian.Permissions.AtomEncoding</tt> and reached through the imported <tt>encode/3</tt> entry point.</p><p><tt>String.to_atom/1</tt> 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 <tt>encode/3</tt> 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 <tt>system_limit</tt>, taking down every application running on it.</p><p>The default encoder is <tt>Guardian.Permissions.BitwiseEncoding</tt>, which is not affected.</p><p>This issue affects guardian: from 2.0.0 before 2.4.1.</p>"}], "value": "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."}], "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": "2026-08-01T18:46:12.113Z"}, "references": [{"tags": ["vendor-advisory", "related"], "url": "https://github.com/ueberauth/guardian/security/advisories/GHSA-fjr5-7xrc-hmpj"}, {"tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-55733.html"}, {"tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-55733"}, {"tags": ["patch"], "url": "https://github.com/ueberauth/guardian/commit/9cd268557846aa4c3ad53566c08f2c190ee5513f"}], "source": {"discovery": "EXTERNAL"}, "title": "Atom-table exhaustion denial of service in Guardian permissions AtomEncoding via unbounded atom creation", "workarounds": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Switch the permission encoder to the default <tt>Guardian.Permissions.BitwiseEncoding</tt> or to <tt>Guardian.Permissions.TextEncoding</tt>, neither of which creates atoms. Alternatively, validate every permission value against the configured <tt>perm_set</tt> allowlist (rejecting unknown values) before passing it to <tt>encode/3</tt>.</p>"}], "value": "Switch the permission encoder to the default Guardian.Permissions.BitwiseEncoding or to Guardian.Permissions.TextEncoding, neither of which creates atoms. Alternatively, validate every permission value against the configured perm_set allowlist (rejecting unknown values) before passing it to encode/3."}], "x_generator": {"engine": "cvelib 1.8.0"}}}}

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