CVE-2026-55734 (GCVE-0-2026-55734)
Vulnerability from cvelistv5 – Published: 2026-08-01 18:46 – Updated: 2026-08-03 16:49
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
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-03 16:49 UTC
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
2 products
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"value": "CWE-770"
}
],
"source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
"type": "Secondary"
}
]
}
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-55734",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-08-03T16:49:36.457207Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-08-03T16:49:54.930Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"exploit"
],
"url": "https://github.com/ueberauth/guardian/security/advisories/GHSA-9qx2-v587-q3gg"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://repo.hex.pm",
"cpes": [
"cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*"
],
"defaultStatus": "unaffected",
"modules": [
"\u0027Elixir.Guardian.Permissions\u0027"
],
"packageName": "guardian",
"packageURL": "pkg:hex/guardian",
"product": "guardian",
"programFiles": [
"lib/guardian/permissions.ex"
],
"programRoutines": [
{
"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"
}
],
"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": [
"\u0027Elixir.Guardian.Permissions\u0027"
],
"packageName": "ueberauth/guardian",
"packageURL": "pkg:github/ueberauth/guardian",
"product": "guardian",
"programFiles": [
"lib/guardian/permissions.ex"
],
"programRoutines": [
{
"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"
}
],
"repo": "https://github.com/ueberauth/guardian",
"vendor": "ueberauth",
"versions": [
{
"lessThan": "8d4efbfc352d30f5fcfc75a4d69a795b0e472724",
"status": "affected",
"version": "b7a6128ca4d0ffb7f7df5219dd982304ff9d6802",
"versionType": "git"
}
]
}
],
"configurations": [
{
"lang": "en",
"supportingMedia": [
{
"base64": false,
"type": "text/html",
"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": [
{
"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": "\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": {
"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": "\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": {
"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": "2026-08-03T16:49:59.913Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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