{"id":"CVE-2026-54894","state":"PUBLISHED","title":"Atom-table exhaustion denial of service in Guardian via unbounded atom creation from binary keys","description":"Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unbounded atom creation from attacker-influenced binary input.\n\nGuardian.Plug.Keys derives connection and session namespace keys by passing arbitrary binaries to String.to_atom/1. base_key/1 in lib/guardian/plug/keys.ex converts any binary into the atom :\"guardian_<input>\", and the derived helpers claims_key/1, resource_key/1, and token_key/1 create a second atom on top of that. key_from_other/1 likewise converts a regex-captured binary through String.to_atom/1. The public specs advertise String.t() as a valid argument, so passing a string is documented usage, and higher-level entry points such as Guardian.Plug.current_token(conn, key: key) thread the caller-supplied key straight into these functions.\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 routes attacker-influenced data (a tenant identifier, header, or other request input) into a Guardian key 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, taking down every application running on it.\n\nThis issue affects guardian: from 0.1.0 before 2.4.1.","publishedAt":"2026-08-01T18:46:05.861Z","updatedAt":"2026-08-03T17:49:54.220Z","severity":{"score":6.9,"label":"Medium","version":"4.0","vector":"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","source":"EEF"},"assigner":"EEF","products":["ueberauth guardian"],"affected":[{"vendor":"ueberauth","product":"guardian","packageName":"guardian","packageURL":"pkg:hex/guardian","defaultStatus":"unaffected","versions":[{"version":"0.1.0","status":"affected","lessThan":"2.4.1","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Guardian.Plug.Keys'"],"programFiles":["lib/guardian/plug/keys.ex"],"programRoutines":[{"name":"'Elixir.Guardian.Plug.Keys':base_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':claims_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':resource_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':token_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':key_from_other/1"}],"repo":"https://github.com/ueberauth/guardian"},{"vendor":"ueberauth","product":"guardian","packageName":"ueberauth/guardian","packageURL":"pkg:github/ueberauth/guardian","defaultStatus":"unaffected","versions":[{"version":"7126fa433afc2563fcac0c9aa35193965f8fd5f8","status":"affected","lessThan":"2952657e42e6341a67e6aaad09d8f0b40ae917cb","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Guardian.Plug.Keys'"],"programFiles":["lib/guardian/plug/keys.ex"],"programRoutines":[{"name":"'Elixir.Guardian.Plug.Keys':base_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':claims_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':resource_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':token_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':key_from_other/1"}],"repo":"https://github.com/ueberauth/guardian"}],"references":["https://github.com/ueberauth/guardian/security/advisories/GHSA-xqch-c77q-rgh5","https://cna.erlef.org/cves/CVE-2026-54894.html","https://osv.dev/vulnerability/EEF-CVE-2026-54894","https://github.com/ueberauth/guardian/commit/2952657e42e6341a67e6aaad09d8f0b40ae917cb"],"weaknesses":["CWE-770"],"ingestedAt":"2026-10-29T20:12:24.861Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/54xxx/CVE-2026-54894.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-54894","state":"PUBLISHED","datePublished":"2026-08-01T18:46:05.861Z","dateUpdated":"2026-08-03T17:49:54.220Z","assignerShortName":"EEF","assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateReserved":"2026-06-16T10:47:13.915Z"},"containers":{"cna":{"title":"Atom-table exhaustion denial of service in Guardian via unbounded atom creation from binary keys","descriptions":[{"lang":"en","value":"Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unbounded atom creation from attacker-influenced binary input.\n\nGuardian.Plug.Keys derives connection and session namespace keys by passing arbitrary binaries to String.to_atom/1. base_key/1 in lib/guardian/plug/keys.ex converts any binary into the atom :\"guardian_<input>\", and the derived helpers claims_key/1, resource_key/1, and token_key/1 create a second atom on top of that. key_from_other/1 likewise converts a regex-captured binary through String.to_atom/1. The public specs advertise String.t() as a valid argument, so passing a string is documented usage, and higher-level entry points such as Guardian.Plug.current_token(conn, key: key) thread the caller-supplied key straight into these functions.\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 routes attacker-influenced data (a tenant identifier, header, or other request input) into a Guardian key 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, taking down every application running on it.\n\nThis issue affects guardian: from 0.1.0 before 2.4.1."}],"affected":[{"vendor":"ueberauth","product":"guardian","packageName":"guardian","packageURL":"pkg:hex/guardian","defaultStatus":"unaffected","versions":[{"version":"0.1.0","status":"affected","lessThan":"2.4.1","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Guardian.Plug.Keys'"],"programFiles":["lib/guardian/plug/keys.ex"],"programRoutines":[{"name":"'Elixir.Guardian.Plug.Keys':base_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':claims_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':resource_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':token_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':key_from_other/1"}],"repo":"https://github.com/ueberauth/guardian"},{"vendor":"ueberauth","product":"guardian","packageName":"ueberauth/guardian","packageURL":"pkg:github/ueberauth/guardian","defaultStatus":"unaffected","versions":[{"version":"7126fa433afc2563fcac0c9aa35193965f8fd5f8","status":"affected","lessThan":"2952657e42e6341a67e6aaad09d8f0b40ae917cb","versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Guardian.Plug.Keys'"],"programFiles":["lib/guardian/plug/keys.ex"],"programRoutines":[{"name":"'Elixir.Guardian.Plug.Keys':base_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':claims_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':resource_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':token_key/1"},{"name":"'Elixir.Guardian.Plug.Keys':key_from_other/1"}],"repo":"https://github.com/ueberauth/guardian"}],"references":[{"url":"https://github.com/ueberauth/guardian/security/advisories/GHSA-xqch-c77q-rgh5","tags":["vendor-advisory","related"]},{"url":"https://cna.erlef.org/cves/CVE-2026-54894.html","tags":["related"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-54894","tags":["related"]},{"url":"https://github.com/ueberauth/guardian/commit/2952657e42e6341a67e6aaad09d8f0b40ae917cb","tags":["patch"]}],"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":{"shortName":"EEF","orgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateUpdated":"2026-08-01T18:46:05.861Z"},"configurations":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<p>Only applications that derive a Guardian key (the conn/session namespace) from attacker-influenced data are exploitable. This is the case when a caller-supplied value such as a tenant identifier, request header, or other request input is passed as the <tt>:key</tt> option to entry points like <tt>Guardian.Plug.current_token/2</tt>. Applications that use a static namespace (the default <tt>:default</tt> key or hardcoded atoms) are not affected.</p>"}],"value":"Only applications that derive a Guardian key (the conn/session namespace) from attacker-influenced data are exploitable. This is the case when a caller-supplied value such as a tenant identifier, request header, or other request input is passed as the :key option to entry points like Guardian.Plug.current_token/2. Applications that use a static namespace (the default :default key or hardcoded atoms) are not affected."}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*","versionEndExcluding":"2.4.1","versionStartIncluding":"0.1.0","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"}],"impacts":[{"capecId":"CAPEC-130","descriptions":[{"lang":"en","value":"CAPEC-130 Excessive Allocation"}]}],"source":{"discovery":"EXTERNAL"},"workarounds":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"<p>Do not derive Guardian keys from untrusted input. Use a fixed, hardcoded set of namespace keys, or validate the value against a bounded allowlist of known keys, before passing it as the <tt>:key</tt> option.</p>"}],"value":"Do not derive Guardian keys from untrusted input. Use a fixed, hardcoded set of namespace keys, or validate the value against a bounded allowlist of known keys, before passing it as the :key option."}],"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/ueberauth/guardian/security/advisories/GHSA-xqch-c77q-rgh5","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-03T17:49:32.217048Z","id":"CVE-2026-54894","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-03T17:49:54.220Z"}}]}}}