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VulnerabilityPublished Updated

CVE-2026-44897: lepture mistune · Cross-site Scripting

Affects lepture mistuneSource CVE Database V5

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Not known to be exploited · CVSS 6.1 Medium : upgrade to 3.2.1 when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score
6.1Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 13% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.2.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 26 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

What to do

Upgrade lepture mistune to 3.2.1.

Affected software

ProductAffectedFixed in
lepturemistuneAffected
  • <3.2.1
Fixed in
  • 3.2.1
PyPImistunepkg:pypi/mistuneOther threatsAffected
  • <3.2.1
Fixed in
  • 3.2.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Mistune to version 3.2.1 or later, where this vulnerability is fixed by properly escaping the id attribute in HTMLRenderer.heading(). Since this is a library vulnerability, applying the official fix by updating the package is the recommended remediation. Patch status is confirmed fixed in version 3.2.1. No alternative mitigations are indicated.

Description

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading() builds the opening <hN> tag by string-concatenating the id attribute value directly into the HTML — with no call to escape(), safe_entity(), or any other sanitisation function. A double-quote character " in the id value terminates the attribute, allowing an attacker to inject arbitrary additional attributes (event handlers, src=, href=, etc.) into the heading element. This vulnerability is fixed in 3.2.1.

References

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