High severity · published Oct 29, 2026
CVE-2019-25781
Python-Markdown 3.0 through 3.11.2 Denial of Service via Link Bracket Parsing
New
7.5
CVSS
–
EPSS
No
On KEV
Description
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Markdown · Python-Markdown
3.0 through 3.11.2 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2019-25781
CVE.org
https://www.cve.org/CVERecord?id=CVE-2019-25781
issue-tracking
https://github.com/Python-Markdown/markdown/issues/798
product
https://github.com/Python-Markdown/markdown
issue-tracking
https://github.com/Python-Markdown/markdown/issues/1654
technical-description
https://github.com/Python-Markdown/markdown/blob/b41e0aaf1181f1a8cb200cf5a815aad7c0020d23/markdown/inlinepatterns.py#L1155-L1172
third-party-advisory
https://www.vulncheck.com/advisories/python-markdown-3.0-through-3.11.2-denial-of-service-via-link-bracket-parsing
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