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CVE-2026-59928

Mistune vulnerability

7.5 HIGHPublic exploitEPSS 0.65%
  1. Published8 Jul 2026

Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, a Markdown document containing many repeated or distinct reference-link definitions causes quadratic work in src/mistune/block_parser.py and the ref_links environment dictionary handling, allowing denial of service through CPU exhaustion. This issue is fixed in version 3.3.0.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Mistune< 3.3.0

Remediation

Fixed in
Mistune≥ 3.3.0

References

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Frequently asked

Is CVE-2026-59928 being actively exploited?

CVE-2026-59928 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.65%.

How severe is CVE-2026-59928?

CVE-2026-59928 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.65% probability of exploitation.

Which products are affected by CVE-2026-59928?

Affected products include Mistune.

How do I fix CVE-2026-59928?

Upgrade affected software to a fixed version, for example Mistune 3.3.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-59928 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.