CVE-2026-33210: Ruby JSON is a JSON implementation for Ruby

This month

CRITICAL 9.1REMOTEUPGRADE

CVE-2026-33210 is a critical-severity flaw (CVSS 9.1) affecting json. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Ruby JSON is a JSON implementation for Ruby. From version 2.14.0 to before versions 2.15.2.1, 2.17.1.2, and 2.19.2, a format string injection vulnerability can lead to denial of service attacks or information disclosure, when the allow_duplicate_key: false parsing option is used to parse user supplied documents. This issue has been patched in versions 2.15.2.1, 2.17.1.2, and 2.19.2.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 41%)
CISA exploited list	No
Weakness	CWE-134
Published	2026-03-20
Last modified	2026-08-21

Publisher (CNA): GitHub, Inc. · Vendor: ruby-lang

Last updated 2026-08-21 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-20 23:16 UTCPublished CVE record published
2026-08-21 13:17 UTCUpdated Record last modified

ruby-lang json UPGRADE

Affected: >= 2.14.0 and < 2.15.2.1 · >= 2.16.0 and < 2.17.1.2 · >= 2.18.0 and < 2.19.2

Fixed in: 2.15.2.1, 2.17.1.2, 2.19.2

Safe to downgrade to: a release before 2.14.0

1. Check installed version

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

2. UPGRADE to 2.15.2.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade json

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 2.14.0 (Debian / Ubuntu)

apt-cache madison json sudo apt install json=<VERSION_BEFORE_2.14.0> sudo apt-mark hold json

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

dnf --showduplicates list json sudo dnf downgrade json-<VERSION_BEFORE_2.14.0> sudo dnf versionlock add json

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.

Advisories and coverage

Official advisories

AlmaLinux Errata: [ALSA-2026:20596] Important: ruby:4.0 security update 2026-05-27

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.

Quick answers

How do I fix CVE-2026-33210?

json: upgrade to 2.15.2.1, 2.17.1.2, 2.19.2. Exact commands for each OS are on this page.

Is CVE-2026-33210 being exploited?

CVE-2026-33210 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-33210 affect?

CVE-2026-33210 affects json. Severity is critical (CVSS 9.1). Ruby JSON is a JSON implementation for Ruby. From version 2.14.0 to before versions 2.15.2.1, 2.17.1.2, and 2.19.2, a format string injection vulnerability can lead to denial of service attacks or information disclosure, when the allow_dupl

How urgent is CVE-2026-33210?

Priority 52/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Ruby vulnerabilities

Related CVEs

CVE-2020-7712 HIGH 7.2 UPGRADE DOWNGRADE This affects the package json before 10.0.0
CVE-2020-10663 HIGH 7.5 UPGRADE MITIGATE The JSON gem through 2.2.0 for Ruby, as used in Ruby 2.4 through 2.4.9, 2.5 through 2.5.7, and 2.6 through 2.6

References

← Back to latest CVEs