What’s Vulnerable › Vulnerabilities

CVE-2026-53666: React Router: Arbitrary Constructor Injection via deserializeErrors() in React Router SSR Hydration

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-27 · updated 2026-10-24
• Weakness: CWE-470

Description

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.

Affected products

• remix-run react-router: from 6.4.0 before 7.18.0 — fixed in 7.18.0

How to fix

Upgrade to a fixed version: remix-run react-router 7.18.0. Check the vendor advisory for mitigations.

References

• https://github.com/remix-run/react-router/blob/main/CHANGELOG.md#v7180
• https://github.com/remix-run/react-router/commit/9d22943fd46c8ae4b08236425fa3549e10e9ad1a
• https://github.com/remix-run/react-router/pull/15175
• https://github.com/remix-run/react-router/releases/tag/react-router@7.18.0
• https://github.com/remix-run/react-router/security/advisories/GHSA-337j-9hxr-rhxg

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