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 e

mediumCVSS 6.1CVE-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.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: medium — CVSS 6.1
Published: 2026-07-27
Last updated: 2026-07-28
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-53666

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-536660.42% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 34% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-53666	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

mediumGHSA-337j-9hxr-rhxg: React Router: Arbitrary Constructor Injection via deserializeErrors() in React Router SSR…ghsa

Recent advisories for React Router is

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

unknownCVE-2026-55685: React Router is a router for React. In versions 7.0.0 through 7.17.0, the manifest endpoint co…nvd · 2026-07-27
unknownCVE-2026-53669: React Router is a router for React. Versions 6.0.0 through 7.17.0 are vulnerable to Open Redir…nvd · 2026-07-27
mediumCVE-2026-53668: React Router is a router for React. In versions 6.30.2 through 6.30.4 and 7.9.6 through 7.12.0…nvd · 2026-07-27
mediumCVE-2026-53667: React Router is a router for React. In versions 7.11.0 through 7.17.0, the RSCErrorHandler is …nvd · 2026-07-27
mediumCVE-2026-64643: Next.js is a React framework for building full-stack web applications. In versions 12.0.0 thro…nvd · 2026-07-27
highCVE-2026-64642: Next.js is a React framework for building full-stack web applications. In versions 16.0.0 thro…nvd · 2026-07-27