Vulnerability · Published Jul 27, 2026 · Assigned by GitHub_M
CVE-2026-53666React Router: Arbitrary Constructor Injection via deserializeErrors() in React Router SSR Hydration
Medium 6.1
In plain English
A medium-severity security flaw in react-router from remix-run. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 37% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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 packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | react-router | 7.18.0 | GHSA-337j-9hxr-rhxg |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| remix-run | react-router | >= 6.4.0, < 7.18.0 |
Weakness: CWE-470 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
References
- https://github.com/remix-run/react-router/security/advisories/GHSA-337j-9hxr-rhxg x_refsource_CONFIRM
- https://github.com/remix-run/react-router/pull/15175 x_refsource_MISC
- https://github.com/remix-run/react-router/commit/9d22943fd46c8ae4b08236425fa3549e10e9ad1a x_refsource_MISC
- https://github.com/remix-run/react-router/blob/main/CHANGELOG.md#v7180 x_refsource_MISC
- https://github.com/remix-run/react-router/releases/tag/react-router@7.18.0 x_refsource_MISC