Reference page — cumulative record through Wednesday, August 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
ueberauth guardian — Atom-table exhaustion denial of service in Guardian permissions AtomEncoding via unbounded atom creation
AV AC AT PR UI VC VI VA CVSS EPSS %ile KEV
L L P N N N N H 6.9 .0027 19.4 —
AFFECTED
Product Versions Fixed
guardian 2.0.0 – —
guardian b7a6128ca4d0ffb7f7df5219dd982304ff9d6802 – —
TIMELINE
Jun 17 Reserved by EEF
Aug 1 EXPLOIT PUBLISHED — CVE-2026-55733 (ueberauth guardian). Public exploit reference added.
Aug 1 Published (CNA: EEF)
Aug 6 EXPLOIT PUBLISHED — CVE-2026-55733 (ueberauth guardian). Public exploit reference added.
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.
Lifecycle
Complete event history — 4 events, chronological
| Date | Event | Detail |
|---|
| June 17, 2026 | Reserved | Reserved by EEF |
| August 1, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-55733 (ueberauth guardian). Public exploit reference added. |
| August 1, 2026 | Published | Published (CNA: EEF) |
| August 6, 2026 | EXPLOIT PUBLISHED | EXPLOIT PUBLISHED — CVE-2026-55733 (ueberauth guardian). Public exploit reference added. |
Affected
Affected products and packages — 2 rows
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| ueberauth | guardian | — | 2.0.0 | — |
| ueberauth | guardian | — | b7a6128ca4d0ffb7f7df5219dd982304ff9d6802 | — |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-55733 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Wednesday, August 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.