---
id: CVE-2026-115352
title: >-
  Mistune before 3.3.0 Quadratic-Time DoS via Unmatched Brackets in Inline
  Parser
summary: >-
  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 p…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-407
vendor: lepture
product: mistune
affected:
  - mistune < 3.3.0
published: '2026-10-22'
updated: '2026-10-22'
sourceUpdated: '2026-10-22T19:13:28.427Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-115352'
references:
  - url: 'https://github.com/lepture/mistune/security/advisories/GHSA-xrpv-r66x-8p7j'
    label: GitHub Security Advisory (GHSA-xrpv-r66x-8p7j)
  - url: >-
      https://www.vulncheck.com/advisories/mistune-before-3.3.0-quadratic-time-dos-via-unmatched-brackets-in-inline-parser
    label: >-
      VulnCheck Advisory: Mistune before 3.3.0 Quadratic-Time DoS via Unmatched
      Brackets in Inline Parser
tags:
  - cve.org
ingestedAt: '2026-10-22T22:00:50.396Z'
---

## Overview

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.

## Affected

- `mistune < 3.3.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.