# league/commonmark: Quadratic-time denial of service when parsing crafted Markdown

Advisory record · `GHSA-2q4p-g7hv-5rgv`

- **Identifiers:** `GHSA-2q4p-g7hv-5rgv` · `CVE-2026-71488` · `PKSA-t21r-vtr5-3mdz`
- **State:** Confirmed
- **Severity:** CVSS 7.5 High
- **Critical:** No
- **Weakness (CWE):** [CWE-407](https://cwe.mitre.org/data/definitions/407.html) · [CWE-1050](https://cwe.mitre.org/data/definitions/1050.html)
- **Tags:** [Denial of service](https://agentprime.io/advisories/tag/dos.md) · [CWE-1050](https://agentprime.io/advisories/tag/cwe-1050.md)
- **Published:** 6 Aug 2026
- **Updated:** 21 Aug 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 6 Aug 2026, 20:37 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `league/commonmark` (Packagist): affected `>=0.6.0, <2.9.0`; fixed in `2.9.0`

## 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

- 7.5 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0063, the 50th percentile, on 5 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 6 Aug 2026. New records show when each source confirmed them.

## Sources

- [GitHub Advisory Database: GHSA-2q4p-g7hv-5rgv](https://github.com/advisories/GHSA-2q4p-g7hv-5rgv)
- [OSV: GHSA-2q4p-g7hv-5rgv](https://osv.dev/vulnerability/GHSA-2q4p-g7hv-5rgv)
- <https://github.com/thephpleague/commonmark/security/advisories/GHSA-2q4p-g7hv-5rgv>
- <https://github.com/thephpleague/commonmark/commit/a6ef6cdc308dfa39a34239c35818e75892a0e6a8>
- <https://github.com/thephpleague/commonmark/commit/a70979ea0d7d3377bd7127536748454a922bf5eb>
- <https://github.com/thephpleague/commonmark/commit/c97b02e5e652b992033b93ba5d6182f706343fc6>
- <https://github.com/thephpleague/commonmark>
- <https://github.com/thephpleague/commonmark/releases/tag/2.9.0>

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-2q4p-g7hv-5rgv>, 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-2q4p-g7hv-5rgv/>. Everything for agents: <https://agentprime.io/llms.txt>.