Vulnerability in Remix-Run React-Router
CVE-2026-53666
React Router is a router for React. In versions 6.4.0 through 7.17.0, if application code was written in a way that allows attacker-supplied input to overwrite certain aspects of errors caught by the SSR process, then it was possible for an attacker to trigger unexpected constructor execution on the client, which would in turn trigger an outbound network request. This is only possible with very specific (and unlikely) application-layer code. Note that this does not impact an application if it is using Declarative Mode. It only impacts Framework Mode and Data Mode applications that perform manual SSR/hydration. This issue has been fixed in version 7.18.0.
EPSS: 0.003 (23.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
Affected products
- Remix-run React-router — versions >= 6.4.0, < 7.18.0
- Shopify React-router
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Third Party Advisory)
- security-advisories@github.com (Patch, x_refsource_MISC, Issue Tracking)
- security-advisories@github.com (Patch, x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-53666?
- CVE-2026-53666 is a medium-severity vulnerability in Remix-Run React-Router, classified under Use of Externally-Controlled Input to Select Classes or Code (Unsafe Reflection). CVSS score: 6.1/10. Published 2026-07-27.
- How severe is CVE-2026-53666?
- Medium severity. CVSS v3 base score is 6.1 out of 10.