High · CVSS 8.7CVE-2026-115352

Mistune before 3.3.0 Quadratic-Time DoS via Unmatched Brackets in Inline ParserCVE-2026-115352

Answer in brief

CVE-2026-115352 records a High severity (CVSS 8.7) vulnerability in Mistune before 3.3.0 Quadratic-Time DoS via Unmatched Brackets in Inline Parser. The current sources do not mark it as known exploited. The current feed maps lepture/mistune (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 22, 2026Updated Oct 22, 2026Source checked Oct 22, 2026First seen by HOL Oct 22, 2026Material review Oct 22, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.7
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps lepture/mistune (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
lepture/mistunegeneric	>=0 <3.3.0	3.3.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for lepture/mistune.
Review the reported fix. Update lepture/mistune to 3.3.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 22, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 22, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 22, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.