CVE-2026-21884
XSS in SSR via ScrollRestoration with getKey/storageKey in Framework Mode.
Is CVE-2026-21884 being exploited?
Not confirmed. CVE-2026-21884 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.54% probability of exploitation in the next 30 days.
How severe is CVE-2026-21884?
CVE-2026-21884 is rated High with a CVSS score of 8.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-21884?
Yes. A fix has been recorded for CVE-2026-21884. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-21884 affect?
CVE-2026-21884 affects react-router <=7.11.0, @remix-run/react <2.17.3 (Framework Mode SSR). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-21884?
Upgrade to react-router 7.12.0+ and @remix-run/react 2.17.3+
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Server-side XSS: arbitrary JS execution in SSR when untrusted content generates keys via getKey/storageKey.
Patch when possible
- affected< 2.17.3
- affected>= 7.0.0 and < 7.12.0
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.