CVE-2019-25781

HIGH 7.5

Python-Markdown 3.0 through 3.11.2 Denial of Service via Link Bracket Parsing

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-407
Vendor	python-markdown
Product	markdown
Published	Oct 29, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Affected Versions

Python-Markdown / Markdown

3.0 ≤ 3.11.2

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/Python-Markdown/markdown/issues/798 github.com: https://github.com/Python-Markdown/markdown github.com: https://github.com/Python-Markdown/markdown/issues/1654 github.com: https://github.com/Python-Markdown/markdown/blob/b41e0aaf1181f1a8cb200cf5a815aad7c0020d23/markdown/inlinepatterns.py#L1155-L1172 vulncheck.com: https://www.vulncheck.com/advisories/python-markdown-3.0-through-3.11.2-denial-of-service-via-link-bracket-parsing

Credits

Anders Kaseorg Muhammadyusuf Dilmurodov (agrresore)