Bug 2573316 (CVE-2026-128069)

Summary:	CVE-2026-128069 rails-html-sanitizer: rails-html-sanitizer: Cross-Site Scripting via concurrent sanitization race condition
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	akostadi, amasferr, dmayorov, ehelms, eshamard, jlledo, jpasqual, juwatts, jvasik, kaycoth, lblicha, mhulan, ogajduse, osousa, pantinor, rblanco, rchan, smallamp, tsedmik, zhunting
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in rails-html-sanitizer. This vulnerability allows a remote attacker to conduct Cross-Site Scripting (XSS) attacks when the application processes HTML concurrently in a multithreaded environment. Because internal allowlists are modified without synchronization across different requests, a strict sanitization request may inherit permissive rules from a concurrent request. Consequently, malicious script elements or attributes may bypass filtering and execute in a victim's browser.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-11-13 17:32:51 UTC

rails-html-sanitizer is responsible for sanitizing HTML fragments in Rails applications. Before 1.7.2, the HTML4 and HTML5 variants of Rails::HTML::SafeListSanitizer reuse one Rails::HTML::PermitScrubber across calls and mutate its tags and attributes without synchronization. In a multithreaded process, concurrent sanitize calls using different tags: or attributes: options can interleave and cause one call to use the other call's allowlist. If a permissive call admits a script element or event-handler attribute, output expected to be sanitized under a stricter policy can retain it and cause cross-site scripting when rendered. Applications that are single-threaded, use one identical allowlist everywhere, or provide a separate scrubber: are not affected. This issue is fixed in version 1.7.2.