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CVE-2026-55734— guardian atom exhaustion in Guardian.Permissions.encode_permissions!/1

Quick assessment

Affected
ueberauth guardian
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

ueberauth Guardian是ueberauth组织开源的一个基于令牌的身份验证库，可用于 Elixir 应用程序。 ueberauth Guardian 2.0.0至2.4.1之前版本存在资源管理错误漏洞，该漏洞源于Guardian.Permissions模块的encode_permissions!/1函数在处理权限映射时未经验证即将键通过String.to_atom转换为原子，导致原子表资源耗尽，攻击者可造成拒绝服务。

CVSS 6.9 · Medium EPSS 0.48% · P39

Affected Version Matrix 2

VendorProduct Version RangeStatus
ueberauth guardian 2.0.0< 2.4.1 affected
b7a6128ca4d0ffb7f7df5219dd982304ff9d6802< 8d4efbfc352d30f5fcfc75a4d69a795b0e472724 affected
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I. Basic Information for CVE-2026-55734

Vulnerability Information
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Vulnerability Title
guardian atom exhaustion in Guardian.Permissions.encode_permissions!/1
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
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: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5
Vulnerability Title
ueberauth Guardian 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
ueberauth Guardian是ueberauth组织开源的一个基于令牌的身份验证库，可用于 Elixir 应用程序。 ueberauth Guardian 2.0.0至2.4.1之前版本存在资源管理错误漏洞，该漏洞源于Guardian.Permissions模块的encode_permissions!/1函数在处理权限映射时未经验证即将键通过String.to_atom转换为原子，导致原子表资源耗尽，攻击者可造成拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ueberauth guardian 2.0.0 ~ 2.4.1 cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*
ueberauth guardian b7a6128ca4d0ffb7f7df5219dd982304ff9d6802 ~ 8d4efbfc352d30f5fcfc75a4d69a795b0e472724 cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*

II. Public POCs for CVE-2026-55734

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III. Intelligence Information for CVE-2026-55734

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Patches & Fixes for CVE-2026-55734 (1)

Vendor Advisories for CVE-2026-55734 (3)

Same Patch Batch · ueberauth · 2026-08-01 · 4 CVEs total

CVE-2026-55735 8.2 HIGH Guardian.revoke/3 acts on unverified token claims, allowing forged-token session revocatio
CVE-2026-54894 6.9 MEDIUM Atom-table exhaustion denial of service in Guardian via unbounded atom creation from binar
CVE-2026-55733 6.9 MEDIUM Atom-table exhaustion denial of service in Guardian permissions AtomEncoding via unbounded

IV. Related Vulnerabilities

Same product: guardian
Same vendor: ueberauth
Same weakness: CWE-770

V. Comments for CVE-2026-55734

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