# Remote code execution in Kramdown

Advisory record · `GHSA-52p9-v744-mwjj`

- **Identifiers:** `GHSA-52p9-v744-mwjj` · `CVE-2021-28834`
- **State:** Confirmed
- **Severity:** CVSS 9.8 Critical
- **Critical:** Yes: CVSS 9+
- **Weakness (CWE):** [CWE-94](https://cwe.mitre.org/data/definitions/94.html)
- **Tags:** [Code injection](https://agentprime.io/advisories/tag/code-injection.md)
- **Published:** 29 Mar 2021
- **Updated:** 17 Feb 2024
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 29 Mar 2021, 16:30 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Critical

Critical, because:

- CVSS score 9.8: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected packages

- `kramdown` (RubyGems): affected `>=1.16.0, <2.3.1`; fixed in `2.3.1`

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 9.8 Critical, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** 0.027, the 86th percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

This record came from the full history of the GitHub Advisory Database, published 29 Mar 2021. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-52p9-v744-mwjj](https://github.com/advisories/GHSA-52p9-v744-mwjj)
- [OSV: GHSA-52p9-v744-mwjj](https://osv.dev/vulnerability/GHSA-52p9-v744-mwjj)
- <https://nvd.nist.gov/vuln/detail/CVE-2021-28834>
- <https://github.com/gettalong/kramdown/pull/708>
- <https://github.com/stanhu/kramdown/commit/d6a1cbcb2caa2f8a70927f176070d126b2422760>
- <https://github.com/stanhu/kramdown/commit/ff0218aefcf00cd5a389e17e075d36cd46d011e2>
- <https://about.gitlab.com/releases/2021/03/17/security-release-gitlab-13-9-4-released/#remote-code-execution-via-unsafe-user-controlled-markdown-rendering-options>
- <https://github.com/gettalong/kramdown/compare/REL_2_3_0...REL_2_3_1>
- <https://gitlab.com/gitlab-org/gitlab/-/commit/179329b5c3c118924fb242dc449d06b4ed6ccb66>
- <https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NJCJVYHPY6LNUFM6LYZIAUIYOMVT5QGV>
- <https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/S3BBLUIDCUUR3NEE4NJLOCCAV3ALQ3O6>
- <https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/SYOLQKFL6IJCQLBXV34Z4TI4O54GESPR>
- <https://www.debian.org/security/2021/dsa-4890>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-52p9-v744-mwjj>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-52p9-v744-mwjj/>. Everything for agents: <https://agentprime.io/llms.txt>.