CVE-2019-25781 PUBLISHED

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

Assigner: VulnCheck
Reserved: 29.10.2026 Published: 29.10.2026 Updated: 29.10.2026

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: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 Score: 8.7

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	None
Attack Complexity	Low	Integrity	None	Integrity	None
Attack Requirements	None	Availability	High	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

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

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	None
User Interaction	None	Availability Impact	High

CVSS 3.1

Product Status

Vendor	Python-Markdown
Product	Markdown
Versions	Default: unaffected affected from 3.0 to 3.11.2 (incl.)

CVE-2019-25781 PUBLISHED

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

Metrics

Product Status

Credits

References

Problem Types