CVE-2026-84371

Received Received - Intake

SVG SMIL Animation URL Injection in ApostropheCMS via sanitize-html

Publication date: 2026-09-01

Last updated on: 2026-09-01

Assigner: GitHub, Inc.

Description

ApostropheCMS is an open-source Node.js content management system, and sanitize-html provides a simple HTML sanitizer with a clear API. From version 1.9.0 until version 2.17.7, packages/sanitize-html/index.js validates an animation value attribute as one flat URL and does not recognize that attributeName selecting href or xlink:href gives the sibling values, from, to, or by attribute SVG SMIL URL semantics. In configurations that allow the animate, animateColor, animateMotion, animateTransform, or set elements, a values list can begin with a safe fragment and contain a later executable destination that survives allowedSchemesAppliedToAttributes checking. When the sanitized SVG is rendered, the browser can copy that later destination into the live link, and a victim who activates the link can execute script in the application's origin. This issue is fixed in version 2.17.7.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-09-01

Last Modified

2026-09-01

Generated

2026-09-02

AI Q&A

2026-09-02

EPSS Evaluated

N/A

NVD

CVE-2026-84371

Affected Vendors & Products

Vendor	Product	Version / Range
apostrophecms	apostrophe	From 1.9.0 (inc) to 2.17.7 (inc)
sanitize-html	sanitize-html	From 1.9.0 (inc) to 2.17.7 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-79	The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

Attack-Flow Graph

Executive Summary

ApostropheCMS and sanitize-html versions 1.9.0 to 2.17.6 have a flaw where SVG animation attributes like animate or set are not properly sanitized. An attacker can craft SVG content with a safe URL followed by a malicious one in the values list. When rendered, the browser may use the malicious URL, allowing script execution in the application's context.

Detection Guidance

This vulnerability requires checking for outdated versions of sanitize-html (versions 1.9.0 to 2.17.6) and ApostropheCMS configurations allowing SVG SMIL elements. Inspect package.json files for sanitize-html versions in the vulnerable range and review application code for SVG sanitization logic.

Impact Analysis

If you use ApostropheCMS with sanitize-html in the affected versions, an attacker could trick you or your users into clicking a link that executes malicious scripts in your application. This could lead to data theft, unauthorized actions, or further compromise of your system.

Compliance Impact

This vulnerability could lead to unauthorized data access or modification, violating GDPR's integrity and confidentiality principles or HIPAA's security requirements. Organizations may face compliance violations if exploited, resulting in fines or legal consequences.

Mitigation Strategies

Upgrade sanitize-html to version 2.17.7 or later to address the SVG SMIL URL sanitization flaw. Review configurations allowing animate, animateColor, animateMotion, animateTransform, or set elements in ApostropheCMS and restrict unsafe attributes.

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