Medium [CVE-2026-84371] stored XSS via SVG SMIL URI-list scheme-policy bypass
This medium-severity Red Hat Linux advisory covers CVE-2026-84371 affecting Cost Management On Premise, Multicluster Engine for Kubernetes, Red Hat Advanced Cluster Management for Kubernetes 2.
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Summary
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.
Improper validation of the animation value attributes in SVG files allows an attacker to bypass scheme filters and embed a malicious script destination within a list of values. When a user interacts with the rendered SVG animation, the embedded script executes in the context of the application, leading to Cross-Site Scripting (XSS).
To exploit this flaw, an attacker needs to trick a user into clicking or interacting with a malicious rendered SVG file, reducing the likelihood of exploitation.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 46 minutes ago·verify at source
- 2.17.7
Official advisory · high-confidence parse· fetched 46 minutes ago·verify at source
Mitigation checklist
- To mitigate this vulnerability, ensure the allowedTags configuration does not contain any of the following elements: animate, animateColor, animateMotion, animateTransform or set.
Official advisory · high-confidence parse· fetched 46 minutes ago·verify at source
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