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TI-2026-53257 Aliases CVE-2026-76098GHSA-6m44-fpc8-c3rq

Mistune has Denial of Service — RecursionError via Excessive Emphasis Markers in Markdown

Priority HIGH 72CWE-674Published · 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 fixed, 1 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-674.

Summary

Mistune is a Python Markdown parser with renderers and plugins. Versions 3.3.0 through 3.3.2 are vulnerable to DoS through deeply nested tokens. HTML rendering creates deeply nested emphasis tokens from consecutive asterisk characters, and recursive rendering in HTMLRenderer.render_token() can exceed Python's recursion limit and raise RecursionError, allowing crafted Markdown to crash a parsing process. This issue is fixed in version 3.3.3

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00488 42nd percentileScored 2026-11-07
Fix Partial mistune (lepture): 3.3.3mistune (PyPI): 3.3.3Red Hat: 3 advisoriesRed Hat: 3 fixed, 1 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
lepturemistune3.3.0 to before 3.3.33.3.3Patch availableCNA
—mistune (PyPI)3.3.0 to before 3.3.33.3.3Patch availableGHSA-6m44-fpc8-c3rq
  • mistune Vendorlepture Affected 3.3.0 to before 3.3.3 Fixed in 3.3.3 Patch available CNA
  • mistune (PyPI) Vendor— Affected 3.3.0 to before 3.3.3 Fixed in 3.3.3 Patch available GHSA-6m44-fpc8-c3rq

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*——lepture
  • cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:* Versions — — ·lepture

Remediation

  • Fix · CNA mistune (lepture) Fixed in 3.3.3
  • Fix · GHSA-6m44-fpc8-c3rq mistune (PyPI) Fixed in 3.3.3 Advisory →

Red Hat 3 advisories

  • RHSA-2026:87410 Released 2026-10-21 · Red Hat rating Critical
    RHOAI 2.25.12 - Red Hat OpenShift AI
    • Red Hat OpenShift AI 2.25 registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-caikit-nlp-rhel9, registry.redhat.io/rhoai/odh-codeflare-operator-rhel9 +47
  • RHSA-2026:86891 Released 2026-10-21 · Red Hat rating Critical
    RHOAI 3.5.2 - Red Hat OpenShift AI
    • Red Hat OpenShift AI 3.5 registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-built-in-detector-rhel9, registry.redhat.io/rhoai/odh-cli-rhel9 +47
  • RHSA-2026:84734 Released 2026-10-19 · Red Hat rating Critical
    RHOAI 3.4.5 - Red Hat OpenShift AI
    • Red Hat OpenShift AI 3.4 registry.redhat.io/rhoai/odh-ai-gateway-payload-processing-rhel9, registry.redhat.io/rhoai/odh-automl-rhel9, registry.redhat.io/rhoai/odh-autorag-rhel9 +47

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat OpenShift AI (RHOAI)AffectedNo fix yet
Red Hat OpenShift AI 2.25Fixed RHSA-2026:87410
Red Hat OpenShift AI 3.4Fixed RHSA-2026:84734
Red Hat OpenShift AI 3.5Fixed RHSA-2026:86891
Not affected: 5 products
  • Migration Toolkit for Applications 8
  • Red Hat OpenShift AI 2.25
  • Red Hat OpenShift AI 3.4
  • Red Hat OpenShift AI 3.5
  • Red Hat OpenShift Container Platform 4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-76098
  2. 2026-10-03 Alias added: GHSA-6m44-fpc8-c3rq
  3. 2026-10-13 Affected versions changed · Red Hat
  4. 2026-10-20 Fix available: RHSA-2026:84734 · Red Hat
  5. 2026-10-20 Fix available: Red Hat OpenShift AI 3.4 · Red Hat
  6. 2026-10-22 Fix available: RHSA-2026:86891 · Red Hat
  7. 2026-10-22 Fix available: RHSA-2026:87410 · Red Hat
  8. 2026-10-23 Fix available: Red Hat OpenShift AI 2.25, Red Hat OpenShift AI 3.5 · Red Hat

References

Advisory 1

Other 5

  • TI-2026-79440 Path traversal in Mistune include directive lets attackers read files CVSS 4.0CRITICAL 9.2
  • TI-2026-36755 Mistune: Potential DoS via quadratic-time parsing in parse_link_text CVSS 4.0HIGH 8.7
  • TI-2026-25521 Mistune ReDoS in LINK_TITLE_RE allows denial of service with crafted Markdown titles CVSS 4.0HIGH 8.7
  • 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-2026-84319 Quadratic-time denial of service in Mistune emphasis processing CVSS 4.0HIGH 8.7
See all 30 →

Sources

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