Vulnerability in Python-Markdown Markdown
CVE-2019-25781
Python-Markdown 3.0 through 3.11.2 contains an algorithmic complexity vulnerability in inline link parsing that allows remote attackers to exhaust CPU through unmatched brackets. Attackers can submit short Markdown containing repeated [ or ![ characters, forcing LinkInlineProcessor.getText() and getLink() into quadratic scans that keep workers busy for minutes.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/Python-Markdown/markdown/issues/798 (issue-tracking)
- github.com/Python-Markdown/markdown (product)
- github.com/Python-Markdown/markdown/issues/1654 (issue-tracking)
- github.com/Python-Markdown/markdown/blob/b41e0aaf1181f1a8cb200cf5a815aad7c0020d… (technical-description)
- www.vulncheck.com/advisories/python-markdown-3.0-through-3.11.2-denial-of-servi… (third-party-advisory)
Frequently asked questions
- What is CVE-2019-25781?
- CVE-2019-25781 is a high-severity vulnerability in Python-Markdown Markdown, classified under Inefficient Algorithmic Complexity. CVSS score: 7.5/10. Published 2026-10-29.
- How severe is CVE-2019-25781?
- High severity. CVSS v3 base score is 7.5 out of 10.