CVE-2026-53666

Summary

React Router: Arbitrary Constructor Injection via deserializeErrors() in React Router SSR Hydration

Severity

medium

CVSS

6.1

EPSS

0.4% (p36)

CWE

CWE-470

Also known as

GHSA-337j-9hxr-rhxg

Published

2026-07-23

Updated

2026-07-23

Advisory details

If application code allows attacker supplied input to overwrite certain aspects of errors caught by the SSR process, then it was possible for attacker to trigger unexpected constructor execution on the client which would trigger outbound network traffic. This is only possible with very specific (and unlikely) application layer code.

[!NOTE] This does not impact your application if you are using Declarative Mode. This only impacts Framework Mode and Data Mode applications doing manual SSR/hydration

References

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

Related advisories

• GHSA-qwww-vcr4-c8h2 — high · npm/react-router
• CVE-2026-55685 — high · npm/react-router
• CVE-2026-34077 — high · npm/react-router
• CVE-2026-42342 — high · npm/react-router
• CVE-2026-42211 — high · npm/react-router
• CVE-2026-33245 — high · npm/react-router
• CVE-2026-53669 — medium · npm/react-router
• CVE-2026-53667 — medium · npm/react-router

Is your project exposed to this? Stateward checks every dependency on every pull request and flags it only if your code actually reaches it.

Summarize with AI

ChatGPTClaudePerplexity