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CVE-2026-44897— Mistune Heading ID Attribute Injection XSS

Quick assessment

Affected
lepture mistune
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

mistune是Hsiaoming Yang个人开发者的一个快速而强大的 Python Markdown 解析器。 Mistune 3.2.1之前版本存在跨站脚本漏洞，该漏洞源于HTMLRenderer.heading()通过字符串拼接将id属性值直接插入HTML标签而未进行转义，攻击者可通过id值中的双引号终止属性，注入任意额外属性。

CVSS 6.1 · Medium EPSS 0.27% · P18

Possible ATT&CK Techniques 1 AI

T1189 · Drive-by Compromise

Affected Version Matrix 1

VendorProduct Version RangeStatus
lepture mistune < 3.2.1 affected
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I. Basic Information for CVE-2026-44897

Vulnerability Information
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Vulnerability Title
Mistune Heading ID Attribute Injection XSS
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5
Vulnerability Title
mistune 跨站脚本漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
mistune是Hsiaoming Yang个人开发者的一个快速而强大的 Python Markdown 解析器。 Mistune 3.2.1之前版本存在跨站脚本漏洞，该漏洞源于HTMLRenderer.heading()通过字符串拼接将id属性值直接插入HTML标签而未进行转义，攻击者可通过id值中的双引号终止属性，注入任意额外属性。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
lepture mistune < 3.2.1 -

II. Public POCs for CVE-2026-44897

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III. Intelligence Information for CVE-2026-44897

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Vendor Advisories for CVE-2026-44897 (1)

Vendor Pages for CVE-2026-44897 (1)

Same Patch Batch · lepture · 2026-05-26 · 5 CVEs total

CVE-2026-44898 6.1 MEDIUM Mistune TOC Anchor Injection XSS
CVE-2026-44708 6.1 MEDIUM Mistune Math Plugin XSS Escape Bypass
CVE-2026-44899 4.7 MEDIUM Mistune Image Directive CSS Injection Vulnerability
CVE-2026-44896 Mistune: XSS via unescaped figclass/figwidth in Figure directive

IV. Related Vulnerabilities

Same product: mistune
Same vendor: lepture
Same weakness: CWE-79

V. Comments for CVE-2026-44897

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