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TI-2026-42730 Aliases CVE-2026-59922GHSA-c8j7-8cv4-2xmq

Regular expression denial of service in lepture mistune

Priority HIGH 72CWE-1333Published · Updated

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: 3 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, a run of closed tilde, equals-sign, or caret marker pairs around a character causes quadratic work in src/mistune/plugins/formatting.py when the strikethrough, mark, or insert plugin scans for matching markers from each possible start position, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

Why it matters now

Exploitation Proof of concept 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: 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
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

VendorProductAffected versionsFixed inStatusSource
lepturemistunebefore 3.3.03.3.0Patch availableCNA
—mistune (PyPI)before 3.3.03.3.0Patch availableGHSA-c8j7-8cv4-2xmq
  • 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-c8j7-8cv4-2xmq

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*before 3.3.0Vulnerablelepture
  • 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-c8j7-8cv4-2xmq mistune (PyPI) Fixed in 3.3.0 Advisory →

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Migration Toolkit for Applications 8AffectedNo fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)AffectedNo fix yet: Fix deferred
Red Hat OpenShift Container Platform 4AffectedNo fix yet: Fix deferred

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-59922
  2. 2026-10-03 Alias added: GHSA-c8j7-8cv4-2xmq
  3. 2026-10-21 EPSS moved to the 50th–90th percentile

References

Exploit 1

Patch 1

Advisory 1

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-2026-42731 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
  • TI-2026-42738 Insufficient verification of data authenticity in lepture mistune CVSS 3.1MEDIUM 4.3
See all 16 →

Sources

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