CVE-2026-49825Network attack vector

Cross-site scripting via missed xlink href sanitization

Published Aug 20, 2026 · Updated Aug 20, 2026

Cross-site scripting in lxml before 6.1.1 and lxml_html_clean before 0.4.5 allows attackers to execute script via xlink:href URLs. Cleaner performs URL-scheme scrubbing by walking links through rewrite_links() and iterlinks(), but iterlinks() only visits attributes named in lxml.html.defs.link_attrs, whose incomplete list omits the namespaced xlink:href attribute used in embedded SVG or MathML content. Exploitation requires an application to sanitize attacker-controlled markup with Cleaner configured as safe_attrs_only=False and then render a surviving link, which can lead to script execution in the consuming application's origin when the link is followed.

CVSS severity8.2
High
EPSS probability0.24%
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 lxml before 6.1.1 and lxml_html_clean before 0.4.5 allows attackers to execute script via xlink:href URLs. Cleaner performs URL-scheme scrubbing by walking links through rewrite_links() and iterlinks(), but iterlinks() only visits attributes named in lxml.html.defs.link_attrs, whose incomplete list omits the namespaced xlink:href attribute used in embedded SVG or MathML content. Exploitation requires an application to sanitize attacker-controlled markup with Cleaner configured as safe_attrs_only=False and then render a surviving link, which can lead to script execution in the consuming application's origin when the link is followed.

The record

CVE
CVE-2026-49825
Published
Aug 20, 2026
Updated
Aug 20, 2026
Vendor
lxml
Product
lxml
Classifications
CWE-79, CWE-184, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 20, 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=< 6.1.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

lxml · lxmlversion=< 6.1.1
fedora-python · lxml_html_cleanversion=< 0.4.5

Published CVSS scores

8.2GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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')
CWE-184Incomplete List of Disallowed Inputs
T1059.007JavaScript

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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