Bug 2553658 (CVE-2026-63430)

Summary: CVE-2026-63430 ammonia: ammonia: Cross-site scripting via improper MathML namespace handling
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: anthomas, blitton, dschmidt, ehelms, ggainey, ikhan, jlanda, jpasqual, juwatts, kshier, mbarnett, mdellweg, mhulan, nmoumoul, osousa, pcreech, rbobbitt, rchan, rhel-process-autobot, simaishi, smallamp, stcannon, tmalecek, watson-tool-maintainers, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in ammonia. This vulnerability allows a remote attacker to conduct cross-site scripting (XSS) by submitting specially crafted markup to an application configured to permit specific Mathematical Markup Language (MathML) tags and raw-text elements. Because ammonia does not correctly handle namespace parsing changes after removing tag attributes, the sanitized output is reinterpreted differently by the web browser. Consequently, an attacker can execute arbitrary JavaScript in the context of a user's browser session when the output is rendered.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2555552, 2555553    
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Description OSIDB Bzimport 2026-10-15 18:33:07 UTC 
ammonia is a Rust library for repairing and securing untrusted HTML. Prior to 3.3.2, 4.0.2, and 4.1.3, applications that explicitly allow the math tag, annotation-xml, and at least one raw-text HTML element while disallowing the encoding attribute can permit mutation cross-site scripting. ammonia does not correctly implement annotation-xml's encoding-dependent MathML integration-point behavior after attribute filtering removes encoding, so the sanitizer validates a descendant under one namespace interpretation while the browser reparses the output under another. An attacker can use that namespace transition and an allowed raw-text HTML element to execute JavaScript when a user renders the sanitized output. The required tags are not enabled by default, so applications that do not explicitly allow them are not affected. This issue is fixed in versions 3.3.2, 4.0.2, and 4.1.3.