CVE-2021-28834

What it is

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

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

2.7% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-03-19 07:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:46 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 2.7% in the next 30 days (EPSS).
• Severity: 9.8 CRITICAL (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-03-19 07:15 UTC

Last modified

2026-06-17 03:46 UTC

Exploit probability

2.7% · EPSS, next 30 days

Record status

Modified

Affected

• Kramdown Project Kramdown < 2.3.1
• Fedoraproject Fedora 32
• Fedoraproject Fedora 33
• Fedoraproject Fedora 34
• Debian Linux 10.0

Attack profile CVSS 3.1 · 9.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-28834.md and follow it. Check whether this project is affected by CVE-2021-28834. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge