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VulnerabilityPublished Updated

CVE-2026-55734: ueberauth guardian · Unthrottled Resource Allocation

Affects ueberauth guardianSource CVE Database V5

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Not known to be exploited · CVSS 6.9 Medium : upgrade to 2.4.1 when convenient.

Data as of 31 Oct 2026, 08:20 UTC

CVSS 4.0 base score
6.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 41% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.4.1, 8d4efbfc352d30f5fcfc75a4d69a795b0e472724
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 1 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade guardian to 2.4.1; guardian to 8d4efbfc352d30f5fcfc75a4d69a795b0e472724.

Affected software

ProductAffectedFixed in
ueberauthguardianAffected
  • >=2.0.0 <2.4.1
Fixed in
  • 2.4.1
ueberauthguardianAffected
  • ≥ b7a6128ca4d0ffb7f7df5219dd982304ff9d6802, < 8d4efbfc352d30f5fcfc75a4d69a795b0e472724
Fixed in
  • 8d4efbfc352d30f5fcfc75a4d69a795b0e472724
Hexguardianpkg:hex/guardianOther threatsAffected
  • >=2.0.0 <2.4.1
Fixed in
  • 2.4.1

CPE configurations (1)

  • cpe:2.3:a:ueberauth:guardian:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, avoid passing untrusted or attacker-controlled data to the encode_permissions!/1 function or related permission encoding routines. Consider implementing input validation or throttling on permission map keys to prevent uncontrolled atom creation.

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.

References

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