# markdown-it linkify: true has two quadratic paths, so a few hundred KB of markdown blocks the event loop for tens of seconds

Advisory record · `GHSA-253c-mchw-3w2r`

- **Identifiers:** `GHSA-253c-mchw-3w2r`
- **State:** Confirmed
- **Severity:** CVSS 4.0, no score published
- **Critical:** No
- **Weakness (CWE):** [CWE-400](https://cwe.mitre.org/data/definitions/400.html) · [CWE-407](https://cwe.mitre.org/data/definitions/407.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md)
- **Published:** 29 Sept 2026
- **Updated:** 29 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 29 Sept 2026, 17:57 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `markdown-it` (npm): affected `>=15.0.0, <15.0.1 || <14.3.1`; fixed in `15.0.1`, `14.3.1`

## 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

- Score not published, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** No score.

## Timeline

- 29 Sept 2026, 17:57 UTC: [Confirmed by GitHub Advisory Database](https://github.com/advisories/GHSA-253c-mchw-3w2r)
- 31 Oct 2026, 13:34 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-253c-mchw-3w2r)

## Sources

- [GitHub Advisory Database: GHSA-253c-mchw-3w2r](https://github.com/advisories/GHSA-253c-mchw-3w2r)
- [OSV: GHSA-253c-mchw-3w2r](https://osv.dev/vulnerability/GHSA-253c-mchw-3w2r)
- <https://github.com/markdown-it/markdown-it/security/advisories/GHSA-253c-mchw-3w2r>
- <https://github.com/markdown-it/markdown-it/commit/09fa07118dda4c953f058848f53dae88395618ca>
- <https://github.com/markdown-it/markdown-it/commit/aaadcfa6d817b3c5f89afb49d97c7b797a6dd4fd>
- <https://github.com/markdown-it/markdown-it/commit/ad70f6b7cff64bee10e42a774147112480ca0d49>
- <https://github.com/markdown-it/markdown-it>

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-253c-mchw-3w2r>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

---

The web page: <https://agentprime.io/advisories/GHSA-253c-mchw-3w2r/>. Everything for agents: <https://agentprime.io/llms.txt>.