CVE-2026-65902

Description

DOMPurify before 3.4.7 passes direct references to the module-level DEFAULT_ALLOWED_TAGS and DEFAULT_ALLOWED_ATTR sets to the uponSanitizeElement and uponSanitizeAttribute hooks via data.allowedTags / data.allowedAttributes when sanitize is called without an explicit cfg.ALLOWED_TAGS / cfg.ALLOWED_ATTR array. A hook that mutates these fields permanently widens the default allow-lists for the lifetime of the DOMPurify instance, so all subsequent default-config sanitize calls inherit the widened defaults and attacker payloads using the poisoned tag/attribute name survive sanitization. removeAllHooks(), clearConfig(), and passing a fresh cfg do not recover the state; only constructing a new DOMPurify instance does.

Weakness classification

• disclosure@vulncheck.com: CWE-501

Primary references

• disclosure@vulncheck.com — Patch
• disclosure@vulncheck.com — Exploit, Third Party Advisory
• disclosure@vulncheck.com — Third Party Advisory
• 134c704f-9b21-4f2e-91b3-4a467353bcc0 — Exploit, Third Party Advisory