CVE-2019-25781
Python-Markdown 3.0 through 3.11.2 Denial of Service via Link Bracket Parsing
- State
- Published
- Severity
- 8.7 High
- Published
- Oct 29, 2026
- Updated
- Oct 29, 2026
- Reserved
- Oct 29, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 7.5 High | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | VulnCheck |
Weaknesses
- CWE-407 Inefficient Algorithmic Complexity
Affected Products
| Product | Versions |
|---|---|
MarkdownPython-Markdown |
|
References
- GitHub Issue #798issue-tracking
- https://github.com/Python-Markdown/markdownproduct
- GitHub Issue #1654issue-tracking
- https://github.com/Python-Markdown/markdown/blob/b41e0aaf1181f1a8cb200cf5a815aad7c0020d23/markdown/inlinepatterns.py#L1155-L1172technical-description
- VulnCheck Advisory: Python-Markdown 3.0 through 3.11.2 Denial of Service via Link Bracket Parsingthird-party-advisory
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