CVE-2026-55733: Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unboun

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HIGH 7.5REMOTEUPGRADE

CVE-2026-55733 is a high-severity flaw (CVSS 7.5) affecting guardian. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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_a

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 60%)
CISA exploited list	No
Weakness	CWE-770
Published	2026-08-01
Last modified	2026-10-23

Publisher (CNA): EEF · Vendor: ueberauth

Am I affected?

Timeline

2026-08-01 19:16 UTCPublished CVE record published
2026-10-23 22:10 UTCUpdated Record last modified

ueberauth guardian UPGRADE

Affected: >= 2.0.0 and < 2.4.1

Fixed in: 2.4.1

Safe to downgrade to: a release before 2.0.0

1. Check installed version

apt-cache policy guardian || rpm -q guardian || guardian --version

2. UPGRADE to 2.4.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade guardian

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade guardian

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 2.0.0 (Debian / Ubuntu)

apt-cache madison guardian sudo apt install guardian=<VERSION_BEFORE_2.0.0> sudo apt-mark hold guardian

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list guardian sudo dnf downgrade guardian-<VERSION_BEFORE_2.0.0> sudo dnf versionlock add guardian

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

Fedora 46 · rubygem-eventmachine · FIXED · 1.2.7-37.fc46 · FEDORA-2026-7194c202a2 · source

sudo dnf upgrade --advisory=FEDORA-2026-7194c202a2

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: cna.erlef.org/cves/CVE-2026-55733.html
Write-up: github.com/ueberauth/guardian/security/advisories/GHSA-fjr5-7xrc-hmpj

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Related CVEs

CVE-2026-54894 HIGH 7.5 UPGRADE Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unboun
CVE-2026-55734 HIGH 7.5 UPGRADE Allocation of Resources Without Limits or Throttling vulnerability in ueberauth guardian (Guardian.Permissions
CVE-2026-55735 HIGH 7.5 UPGRADE Improper Verification of Cryptographic Signature in ueberauth guardian allows an unauthenticated attacker to r

References

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