PT-2021-5816 · Kramdown+4 · Kramdown+4

Stan Hu · Published 2021-03-14 · Updated 2026-03-13 · CVE-2021-28834

Positive Technologies (AI Summary)

CVSS v3.1

9.8

Critical

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Name of the Vulnerable Software and Affected Versions Kramdown versions prior to 2.3.1

Description The issue is related to the lack of restriction of Rouge formatters to the Rouge::Formatters namespace, allowing arbitrary classes to be instantiated. This could potentially enable a remote attacker to access confidential data, compromise its integrity, and cause a denial of service.

Recommendations For versions prior to 2.3.1, update to version 2.3.1 or later to resolve the issue. As a temporary workaround, consider restricting access to the Rouge formatters to minimize the risk of exploitation.

Exploit

Fix

Code Injection

Weakness Enumeration

CWE-94

CWE-470

Related Identifiers

ALT-PU-2021-1602

BDU:2022-00305

CVE-2021-28834

DSA-4890-1

GHSA-52P9-V744-MWJJ

OESA-2021-1159

OPENSUSE-SU-2024:11336-1

OPENSUSE-SU-2024:12038-1

OPENSUSE-SU-2024:13161-1

OPENSUSE-SU-2024:14170-1

OPENSUSE-SU-2025:15119-1

OPENSUSE-SU-2026:10352-1

USN-6424-1

Affected Products

Alt Linux

Astra Linux

Kramdown

Linuxmint

Ubuntu

References · 43

• 🔥 https://github.com/gettalong/kramdown/pull/708 · Exploit
• https://github.com/gettalong/kramdown/compare/REL_2_3_0...REL_2_3_1 · Patch
• https://bdu.fstec.ru/vul/2022-00305 · Security Note
• https://wiki.astralinux.ru/astra-linux-se17-bulletin-2021-1126SE17 · Vendor Advisory
• https://ubuntu.com/security/CVE-2021-28834 · Vendor Advisory
• https://osv.dev/vulnerability/openSUSE-SU-2024:14170-1 · Vendor Advisory
• https://osv.dev/vulnerability/USN-6424-1 · Vendor Advisory
• https://osv.dev/vulnerability/openSUSE-SU-2026:10352-1 · Vendor Advisory
• https://debian.org/security/2021/dsa-4890 · Vendor Advisory
• https://lists.fedoraproject.org/archives/list/[e-mail]/message/NJCJVYHPY6LNUFM6LYZIAUIYOMVT5QGV · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2021-28834 · Security Note
• https://osv.dev/vulnerability/GHSA-52p9-v744-mwjj · Vendor Advisory
• https://osv.dev/vulnerability/openSUSE-SU-2025:15119-1 · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2021-28834 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2021-28834 · Vendor Advisory