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

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

• 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
• OSV: GHSA-2q4p-g7hv-5rgv
• github.com/thephpleague/commonmark/security/advisories/GHSA-2q4p-g7hv-5rgv
• github.com/thephpleague/commonmark/commit/a6ef6cdc308dfa39a34239c35818e75892a0e6a8
• github.com/thephpleague/commonmark/commit/a70979ea0d7d3377bd7127536748454a922bf5eb
• github.com/thephpleague/commonmark/commit/c97b02e5e652b992033b93ba5d6182f706343fc6
• github.com/thephpleague/commonmark
• 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.