Bug 2520556

Summary: CVE-2026-65898 nextcloud: DOMPurify: Cross-site scripting via permanent attribute allowlist pollution [epel-all]
Product: [Fedora] Fedora EPEL Reporter: Ganesh <gnaik>
Component: nextcloudAssignee: Andrew Bauer <zonexpertconsulting>
Status: CLOSED CURRENTRELEASE QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: medium    
Version: epel10CC: pampelmuse, zonexpertconsulting
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["c2e04916-ac6b-4c4c-99cc-bc8e4232b943"]}
Fixed In Version: Doc Type: ---
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2026-08-20 16:57:49 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 2506436    

Description Ganesh 2026-08-20 16:50:26 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

DOMPurify before 3.4.11 fails to clone the ALLOWED_ATTR allowlist when setConfig() is used with an uponSanitizeAttribute hook, allowing the hook to permanently mutate the shared allowlist. Attackers can register a hook that conditionally allows dangerous attributes like onerror for trusted elements, then submit untrusted content that inherits the polluted allowlist and executes event handlers as stored XSS.
Comment 1 Andrew Bauer 2026-08-20 16:57:49 UTC 
This bug is not valid. As of this writing, the current Nextcloud 34.0.3 release contain DOMPurify 3.4.13 which does not contain this CVE.

See:
https://github.com/nextcloud/server/blob/v34.0.3/package-lock.json#L6512