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🐍 PyPI
Not in CISA KEV
HIGH severity

CVE-2022-34749 — mistune

HIGHFix: lepture/mistune@a6d4321

CVE-2022-34749 is a high-severity (CVSS 8.6) CWE-1333 vulnerability in mistune. A fix is available for mistune — see the affected versions and patch details below.

Mistune vulnerable to catastrophic backtracking

Also known asGHSA-fw3v-x4f2-v673PYSEC-2022-237
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs76th percentile — riskier than 76% of all scored CVEsHighest risk
0.02%0.72%1.42%2.12%0.5%1.6%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐍mistune

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

In mistune through 2.0.2, support of inline markup is implemented by using regular expressions that can involve a high amount of backtracking on certain edge cases. This behavior is commonly named catastrophic backtracking.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPImistune≥ 2.0.0a1&&< 2.0.32.0.3pip install --upgrade 'mistune==2.0.3'

Affected Products

2 products · 2 configurations
OS
fedorafedoraproject
1 version
37
Application
mistunemistune_project
≤ 2.0.2
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mistune, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update mistune to 2.0.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-34749 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This vulnerability is rated as Moderate impact because successful exploitation results in application denial of service through excessive CPU resource consumption, without compromising system confidentiality or data integrity. In Red Hat environments, the mistune library is utilized by integrated platform services to…

ProductFixed inAdvisory
Red Hat Ceph Storage 7.1ceph-2:18.2.1-381.el8cpRHSA-2026:2769
Red Hat Ceph Storage 8.1ceph-2:19.2.1-331.el9cpRHSA-2026:2711
Red Hat Ceph Storage 8rhceph/rhceph-8-rhel9:1770630907RHSA-2026:2737

Frequently Asked Questions

In mistune through 2.0.2, support of inline markup is implemented by using regular expressions that can involve a high amount of backtracking on certain edge cases. This behavior is commonly named catastrophic backtracking.
O3 Security · Impact-Aware SCA

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CVE-2022-34749: mistune — Fixed in 2.0.3