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Vulnerabilities / CVE-2021-28834

critical

CVE-2021-28834

rubygem-kramdown: allows arbitrary classes to be instantiated

Published Modified
In the Trivy database since at least 24 Oct 2026, 07:11 UTCWhen it arrived before that build is not recorded.

Severity by source

NVD9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
GHSA9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Red Hat9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Trivy's own label is CRITICAL. Rated critical by NVD, Ruby Advisory DB. Rated lower by GHSA (high), Red Hat (medium), Ubuntu (medium).

Description

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

Affected packages and fixed versions

SourcePackageFixed in
rubygems::Ruby Advisory Databasekramdown>= 2.3.1
debian 10ruby-kramdown1.17.0-1+deb10u2
debian 11ruby-kramdown2.3.0-5
debian 12ruby-kramdown2.3.0-5
debian 13ruby-kramdown2.3.0-5
debian 14ruby-kramdown2.3.0-5
echoruby-kramdown2.3.0-5
rubygems::GitHub Security Advisory RubyGemskramdown2.3.1
ubuntu 20.04ruby-kramdown1.17.0-4ubuntu0.2
ubuntu 20.04-ESMruby-kramdown1.17.0-4ubuntu0.2

References

All 18 references

Vulnerability data compiled from the Trivy vulnerability database (trivy-db, Aqua Security, Apache License 2.0), which aggregates third-party advisories. CVE records are published by The MITRE Corporation under the CVE Terms of Use; CVE is a trademark of MITRE. This product uses data from the NVD API but is not endorsed or certified by the NVD. Severity, titles and advisory data from the GitHub Advisory Database (CC BY 4.0), Red Hat security data (CC BY 4.0) and the other sources linked on each entry. Entries may be summarised or re-formatted; the linked original is the authoritative record.