CVE-2026-55733: ueberauth guardian · Unthrottled Resource Allocation
Affects ueberauth guardianSource CVE Database V5
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
- 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, 9cd268557846aa4c3ad53566c08f2c190ee5513f
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:HExploitation evidence
Disclosed: evidence found.
CVE published 1 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 9cd268557846aa4c3ad53566c08f2c190ee5513f.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| ueberauthguardian | Affected
| Fixed in
|
| ueberauthguardian | Affected
| Fixed in
|
Hexguardianpkg:hex/guardianOther threats | Affected
| Fixed in
|
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 using Guardian.Permissions.AtomEncoding for encoding permission scopes with untrusted input. Prefer the default Guardian.Permissions.BitwiseEncoding encoder or implement input validation and allow-listing to prevent unbounded atom creation.
Description
Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unbounded atom creation from attacker-controlled binary input. Guardian.Permissions.AtomEncoding encodes permission scopes by passing arbitrary binaries to String.to_atom/1. When encode/3 in lib/guardian/permissions/atom_encoding.ex is called with a list, each binary entry is handled by the encode_value/3 binary clause, which calls String.to_atom(value) with no allow-list check. The perm_set argument (the application's small, finite set of legitimate permission names) is discarded, so any external string flows straight into atom creation. This encoder is selected with use Guardian.Permissions, encoding: Guardian.Permissions.AtomEncoding and reached through the imported encode/3 entry point. String.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 funnels attacker-influenced permission scopes (from a request body, a JWT claim, or other external input) into encode/3 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 with system_limit, taking down every application running on it. The default encoder is Guardian.Permissions.BitwiseEncoding, which is not affected. This issue affects guardian: from 2.0.0 before 2.4.1.
References
- github.com/ueberauth/guardian/security/advisories/GHSA-fjr5-7xrc-hmpj (opens in a new tab)
- cna.erlef.org/cves/CVE-2026-55733.html (opens in a new tab)
- osv.dev/vulnerability/EEF-CVE-2026-55733 (opens in a new tab)
- github.com/ueberauth/guardian/commit/9cd268557846aa4c3ad53566c08f2c190ee5513f (opens in a new tab)