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.

CVSS 4.0

8.7CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE

CWE-407

Published

2026-10-29

Modified

2026-10-29

Record from

the NVD, synced 2026-10-29

References

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

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