$ cve CVE-2021-28834 JSON

CVE-2021-28834

9.8

CRITICAL · CVSS 3.1 · EPSS 2.8% (pctl 86)

In your normal cycle

Critical by CVSS (9.8), but no sign of active exploitation.

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

CVSS	9.8 (CRITICAL, v3.1)
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS	2.81% — more likely to be exploited than 86% of all CVEs
On CISA KEV	no
Public exploit	none known
Published	2021-03-19
Last modified	2026-06-17