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CVE-2026-49825— lxml: javascript: URL bypass in Cleaner via xlink:href

Quick assessment

Affected
lxml lxml
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

lxml是lxml团队开源的一个XML和HTML解析库。 lxml 6.1.1之前版本和lxml_html_clean 0.4.5之前版本存在安全漏洞，该漏洞源于lxml.html.defs.link_attrs中的链接属性缺少xlink:href，可能导致嵌入SVG/MathML等内容时发生URL绕过攻击。

CVSS 8.2 · High EPSS 0.30% · P22

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 2

VendorProduct Version RangeStatus
fedora-python lxml_html_clean < 0.4.5 affected
lxml lxml < 6.1.1 affected
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I. Basic Information for CVE-2026-49825

Vulnerability Information
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Vulnerability Title
lxml: javascript: URL bypass in Cleaner via xlink:href
Source: CVE Program / CVE List V5
Vulnerability Description
lxml is a library for processing XML and HTML in the Python language. Prior to 6.1.1, link attributes in ``lxml.html.defs.link_attrs`` were missing ``xlink:href``, which can be used for URL bypass attacks in embedded SVG/MathML/etc. content. This vulnerability was fixed in lxml 6.1.1 and lxml_html_clean 0.4.5.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/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
lxml 输入验证错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
lxml是lxml团队开源的一个XML和HTML解析库。 lxml 6.1.1之前版本和lxml_html_clean 0.4.5之前版本存在安全漏洞，该漏洞源于lxml.html.defs.link_attrs中的链接属性缺少xlink:href，可能导致嵌入SVG/MathML等内容时发生URL绕过攻击。
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
lxml lxml < 6.1.1 -
fedora-python lxml_html_clean < 0.4.5 -

II. Public POCs for CVE-2026-49825

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Reproduced successfully in a real sandbox · Below is the actual recording of building the environment and exploiting the vulnerability.
Success marker: VULNERABLE: javascript: URL bypassed lxml Cleaner; proof token exfiltrated: PROOF_f051804e047a6b04
Reproduction recording is a Pro+ exclusive
Watch the full sandbox build + live exploit recording for this CVE. Limited-time ¥499/mo.
Upgrade to Pro+
claude_code · 6433 chars
GitHub 复现环境（可 clone 直接跑）
Pro+ exclusive includes:
Vulnerability reproduction recording (real sandbox build + trigger, exclusive)
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Full executable POC code
Exploit chain & mitigation
POC zip download
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III. Intelligence Information for CVE-2026-49825

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Patches & Fixes for CVE-2026-49825 (3)

Vendor Advisories for CVE-2026-49825 (1)

Vendor Pages for CVE-2026-49825 (1)

IV. Related Vulnerabilities

Same product: lxml
Same vendor: lxml
Same weakness: CWE-79