CVE-2026-115352

High

Description

Mistune before 3.3.0 contains an algorithmic complexity vulnerability in the inline link parser that allows unauthenticated attackers to exhaust CPU by submitting long runs of unmatched '[' characters. Attackers can send small markdown payloads that trigger O(N^2) parse_link_text and parse_link_label probing, occupying rendering workers for 30+ seconds per 16 KB input.

SeverityHigh

CVSS7.5

Exploit probability—

ProductLepture Mistune

PublishedOct 22, 2026

First seenOct 22, 2026

Weakness typeCWE-407CWE-407

How to fix

Update

lepture mistune3.3.0 or later

Vendor advisories

github.com/lepture/mistune/security/advisories/GHSA-xrpv-r66x-8p7j

Affected products

Product	Affected versions	Fixed in
lepture mistune	v < 3.3.0	3.3.0

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