CVE-2026-59926Network attack vector

Cross-site scripting via unescaped Admonition class option

Published Jul 8, 2026 · Updated Jul 8, 2026

Cross-site scripting in Lepture Mistune 3.2.0 and earlier allows remote attackers to inject script via an Admonition class option. render_admonition() appends the raw :class: directive value to a section element's class attribute without HTML escaping, even when renderer escape mode is enabled. Exploitation requires an application to enable the Admonition directive, render attacker-controlled Markdown, and present the output to a user, allowing script execution in that application's origin.

CVSS severity5.3
Medium
EPSS probability0.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Lepture Mistune 3.2.0 and earlier allows remote attackers to inject script via an Admonition class option. render_admonition() appends the raw :class: directive value to a section element's class attribute without HTML escaping, even when renderer escape mode is enabled. Exploitation requires an application to enable the Admonition directive, render attacker-controlled Markdown, and present the output to a user, allowing script execution in that application's origin.

The record

CVE
CVE-2026-59926
Published
Jul 8, 2026
Updated
Jul 8, 2026
Vendor
Lepture
Product
Mistune
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.2.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Lepture · Mistuneversion=< 3.2.1

Published CVSS scores

5.3GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007Command and Scripting Interpreter: JavaScript

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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