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Medium

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

  • Disclosed: 23.07.2026
  • Updated: 11.10.2026 10:22

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

Affected software

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PlatformPackageVulnerable versionsFixed in
npm package react-router >= 6.4.0, < 7.18.0 7.18.0

References

CVSS score 6.1/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness (CWE)
CWE-470
Platform
npm
Package
react-router
Disclosed
23.07.2026
Updated
11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-337j-9hxr-rhxg - CC BY 4.0

Vulnerability history: react-router

All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (20) in the archive
Total entries
20
First → latest
04.2025 07.2026
Without a fix
0
Exploited in attacks
0

Severity breakdown

  • High 11
  • Medium 8
  • Low 1

Disclosures per year

Severity:
  1. React Router: RSC Mode CSRF Bypass Allows Action Execution Before 400 Response
    High ghsa-qwww-vcr4-c8h2 >= 7.12.0, < 7.18.2, >= 8.0.0, < 8.3.0 7.18.2, 8.3.0
  2. React Router: Unauthenticated Denial of Service via Inefficient Route Matching
    High CVE-2026-55685 >= 7.0.0, < 7.18.0 7.18.0
  3. React Router: Arbitrary Constructor Injection via deserializeErrors() in React Router SSR Hydration this entry
    Medium · 6.1 CVE-2026-53666 >= 6.4.0, < 7.18.0 7.18.0
  4. React Router vulnerable to Denial of Service via reflected user input in single-fetch
    High · 7.5 CVE-2026-34077 >= 7.0.0, < 7.14.0 7.14.0
  5. React Router vulnerable to DoS via unbounded path expansion in __manifest endpoint
    High · 7.5 CVE-2026-42342 >= 7.0.0, < 7.15.0 7.15.0
  6. React Router's vendored turbo-stream v2 allows arbitrary constructor invocation via TYPE_ERROR deserialization leading to Unauth RCE
    High · 8.1 CVE-2026-42211 >= 7.0.0, < 7.14.2 7.14.2
  7. React Router vulnerable to XSS in unstable RSC redirect handling via javascript: redirect targets
    High · 8.0 CVE-2026-33245 >= 7.7.0, < 7.13.2 7.13.2
  8. React Router vulnerable to XSS via Open Redirects
    High · 8.0 CVE-2026-22029 >= 7.0.0, < 7.12.0 7.12.0
  9. React Router SSR XSS in ScrollRestoration
    High · 8.2 CVE-2026-21884 >= 7.0.0, < 7.12.0 7.12.0
  10. React Router has XSS Vulnerability
    High · 7.6 CVE-2025-59057 >= 7.0.0, < 7.9.0 7.9.0
  11. React Router allows pre-render data spoofing on React-Router framework mode
    High · 8.2 CVE-2025-43865 >= 7.0.0-pre.0, < 7.5.2 7.5.2
  12. React Router allows a DoS via cache poisoning by forcing SPA mode
    High · 7.5 CVE-2025-43864 >= 7.2.0, < 7.5.2 7.5.2

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