CRITICAL

CVE-2021-28834

CVSS v3

9.8

CRITICAL

EPSS Score

2.7 %

exploit probability, as of 2026-10-19

CISA KEV

known exploited

Exploitation

—

SSVC status

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Affected and fixed versions

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

kramdownRubyGemsfrom 1.16.0 · fixed in 2.3.1

Vendor advisories

CVE-2021-28834 Red Hat Product Security
rubygem-kramdown: allows arbitrary classes to be instantiated

Full record on NVD

Description

Kramdown before 2.3.1 does not restrict Rouge formatters to the Rouge::Formatters namespace, and thus arbitrary classes can be instantiated.

Technical details

Published: 2021-03-19

Frequently asked questions

What is CVE-2021-28834?

Kramdown before 2.3.1 does not restrict Rouge formatters to the Rouge::Formatters namespace, and thus arbitrary classes can be instantiated.

Is CVE-2021-28834 actively exploited?

Active exploitation of CVE-2021-28834 has not been confirmed. Its EPSS score was 2.7% on 2026-10-19, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-28834?

CVE-2021-28834 has a CVSS v3 base score of 9.8 (CRITICAL severity).

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