CVE-2026-55734 (GCVE-0-2026-55734)
Vulnerability from cvelistv5 – Published: 2026-08-01 18:46 – Updated: 2026-08-01 18:46
VLAI
EPSS
VEX
Title
guardian atom exhaustion in Guardian.Permissions.encode_permissions!/1
Summary
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.
Severity
CWE
- CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
4 references
| URL | Tags |
|---|---|
| https://github.com/ueberauth/guardian/security/ad… | vendor-advisoryrelated |
| https://cna.erlef.org/cves/CVE-2026-55734.html | related |
| https://osv.dev/vulnerability/EEF-CVE-2026-55734 | related |
| https://github.com/ueberauth/guardian/commit/8d4e… | patch |
Impacted products
Credits
{
"containers": {
"cna": {
"affected": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"
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"modules": [
"\u0027Elixir.Guardian.Permissions\u0027"
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"packageURL": "pkg:hex/guardian",
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"name": "\u0027Elixir.Guardian.Permissions\u0027:encode_permissions!/1"
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{
"name": "\u0027Elixir.Guardian.Permissions\u0027:encode_permissions_into_claims!/2"
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{
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"vendor": "ueberauth",
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{
"name": "\u0027Elixir.Guardian.Permissions\u0027:encode_permissions!/1"
},
{
"name": "\u0027Elixir.Guardian.Permissions\u0027:encode_permissions_into_claims!/2"
},
{
"name": "\u0027Elixir.Guardian.Permissions\u0027:do_encode_permissions!/2"
}
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"repo": "https://github.com/ueberauth/guardian",
"vendor": "ueberauth",
"versions": [
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"status": "affected",
"version": "b7a6128ca4d0ffb7f7df5219dd982304ff9d6802",
"versionType": "git"
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"lang": "en",
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"value": "\u003cp\u003eThis vulnerability is only exploitable in applications that use \u003ctt\u003eGuardian.Permissions\u003c/tt\u003e (via \u003ctt\u003euse Guardian.Permissions\u003c/tt\u003e) and route attacker-influenced data into \u003ctt\u003eencode_permissions!/1\u003c/tt\u003e or \u003ctt\u003eencode_permissions_into_claims!/2\u003c/tt\u003e, for example by reading a permissions map from a request body and passing it into token issuance.\u003c/p\u003e"
}
],
"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": [
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"criteria": "cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*",
"versionEndExcluding": "2.4.1",
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"vulnerable": true
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"operator": "OR"
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],
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],
"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": [
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"lang": "en",
"supportingMedia": [
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"value": "\u003cp\u003eAllocation of Resources Without Limits or Throttling vulnerability in ueberauth guardian (\u003ctt\u003eGuardian.Permissions\u003c/tt\u003e module) allows a denial of service via BEAM atom-table exhaustion.\u003c/p\u003e\u003cp\u003eThis vulnerability is associated with program file \u003ctt\u003elib/guardian/permissions.ex\u003c/tt\u003e and program routines \u003ctt\u003e\u0027Elixir.Guardian.Permissions\u0027:encode_permissions!/1\u003c/tt\u003e, \u003ctt\u003e\u0027Elixir.Guardian.Permissions\u0027:encode_permissions_into_claims!/2\u003c/tt\u003e, \u003ctt\u003e\u0027Elixir.Guardian.Permissions\u0027:do_encode_permissions!/2\u003c/tt\u003e.\u003c/p\u003e\u003cp\u003eThe \u003ctt\u003eGuardian.Permissions\u003c/tt\u003e mixin installs a public \u003ctt\u003eencode_permissions!/1\u003c/tt\u003e function on every module that does \u003ctt\u003euse Guardian.Permissions\u003c/tt\u003e. For each key of the supplied map, \u003ctt\u003eencode_permissions!/1\u003c/tt\u003e calls \u003ctt\u003eString.to_atom(to_string(k))\u003c/tt\u003e before any validation runs. The integer-value clause of \u003ctt\u003edo_encode_permissions!/2\u003c/tt\u003e 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 \u003ctt\u003eencode_permissions!/1\u003c/tt\u003e (for example a permissions map read from a request body and passed into token issuance via \u003ctt\u003eencode_permissions_into_claims!/2\u003c/tt\u003e) 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 \u003ctt\u003edecode_permissions/1\u003c/tt\u003e is not affected because it skips keys absent from the configured permission set.\u003c/p\u003e\u003cp\u003eThis issue affects guardian: from 2.0.0 before 2.4.1.\u003c/p\u003e"
}
],
"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 \u0027Elixir.Guardian.Permissions\u0027:encode_permissions!/1, \u0027Elixir.Guardian.Permissions\u0027:encode_permissions_into_claims!/2, \u0027Elixir.Guardian.Permissions\u0027: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": {
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"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",
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"vulnConfidentialityImpact": "NONE",
"vulnIntegrityImpact": "NONE"
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"format": "CVSS",
"scenarios": [
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"lang": "en",
"value": "GENERAL"
}
]
}
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"problemTypes": [
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"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": "\u003cp\u003eBefore calling \u003ctt\u003eencode_permissions!/1\u003c/tt\u003e or \u003ctt\u003eencode_permissions_into_claims!/2\u003c/tt\u003e, 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.\u003c/p\u003e"
}
],
"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": {
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"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"
},
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"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-55734",
"date": "2026-08-03",
"epss": "0.00129",
"percentile": "0.02943"
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"nvd": "{\"cve\":{\"id\":\"CVE-2026-55734\",\"sourceIdentifier\":\"6b3ad84c-e1a6-4bf7-a703-f496b71e49db\",\"published\":\"2026-08-01T19:16:42.333\",\"lastModified\":\"2026-08-01T19:16:42.333\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"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 \u0027Elixir.Guardian.Permissions\u0027:encode_permissions!/1, \u0027Elixir.Guardian.Permissions\u0027:encode_permissions_into_claims!/2, \u0027Elixir.Guardian.Permissions\u0027: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. 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}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
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