TI-2026-42733 Aliases CVE-2026-59925 GHSA-4j32-57v6-6g45

inline_parser: quadratic-time parsing on long runs of `x` and `x` emphasis pairs

MEDIUM 40CWE-1333Published 2026-07-08 · Updated 2026-07-08

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Partial Red Hat: 4 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-1333.

Summary

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, long sequences of well-formed double-asterisk or triple-asterisk emphasis pairs around a character cause quadratic work in src/mistune/inline_parser.py because the parser scans forward for matching close markers from every potential opening run, allowing denial of service in default Mistune parsing. This issue is fixed in version 3.3.0.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00644 51st percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by NVD

Fix Partial mistune (lepture): 3.3.0mistune (PyPI): 3.3.0Red Hat: 4 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
lepture	mistune	before 3.3.0	3.3.0	Patch available	CNA
—	mistune (PyPI)	before 3.3.0	3.3.0	Patch available	GHSA-4j32-57v6-6g45

mistune Vendorlepture Affected before 3.3.0 Fixed in 3.3.0 Patch available CNA
mistune (PyPI) Vendor— Affected before 3.3.0 Fixed in 3.3.0 Patch available GHSA-4j32-57v6-6g45

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:mistune_project:mistune::::::::	before 3.3.0	Vulnerable	lepture

cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:* Versions before 3.3.0 Vulnerable ·lepture

Remediation

Fix · CNA mistune (lepture) Fixed in 3.3.0
Fix · GHSA-4j32-57v6-6g45 mistune (PyPI) Fixed in 3.3.0 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

Product	Status	Plan or fix
Migration Toolkit for Applications 8	Affected	No fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)	Affected	No fix yet: Fix deferred
Red Hat OpenShift Container Platform 4	Affected	No fix yet: Fix deferred
Red Hat Satellite 6	Affected	No fix yet: Fix deferred

Timeline

2026-10-02 Threatist record created from CVE-2026-59925
2026-10-03 Alias added: GHSA-4j32-57v6-6g45
2026-10-21 EPSS moved to the 50th–90th percentile

References

Other 3

TI-2026-42736 Mistune block_parser: quadratic-time parsing on long lists of repeated reference-link definitions CVSS 3.1HIGH 7.5
TI-2026-42730 Regular expression denial of service in lepture mistune CVSS 3.1HIGH 7.5
TI-2026-42731 Mistune: XSS via percent-encoded javascript URI bypass in safe_url() CVSS 3.1MEDIUM 6.1
TI-2026-32774 Mistune Image Directive CSS Injection Vulnerability CVSS 3.1MEDIUM 6.1
TI-2026-32773 Mistune TOC Anchor Injection XSS CVSS 3.1MEDIUM 6.1
TI-2026-32595 Mistune Math Plugin XSS Escape Bypass CVSS 3.1MEDIUM 6.1

See all 16 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences