Critical severity (CVSS 9.1) and widespread use of React Router/Remix libraries; high risk for web apps.
CVE-2025-61686
Session storage path traversal in unsigned cookies (React Router/Remix).
Is CVE-2025-61686 being exploited?
Not confirmed. CVE-2025-61686 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 18% probability of exploitation in the next 30 days.
How severe is CVE-2025-61686?
CVE-2025-61686 is rated Critical with a CVSS score of 9.1. 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-2025-61686?
Yes. A fix has been recorded for CVE-2025-61686. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2025-61686 affect?
CVE-2025-61686 affects @react-router/node, @remix-run/node, @remix-run/deno, Remix v2. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2025-61686?
Upgrade to patched versions: @react-router/node 7.9.4+ / Remix 2.17.2+
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Server-side session reads/writes may access files outside the session dir when unsigned cookies are used; depends on server perms.
Immediate action required
- affected>= 7.0.0 and < 7.9.4
- affected< 2.17.2
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.