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CVE-2026-53666 remix-run CVE debrief

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-27T22:17:30.937Z and has not been modified since then. CVE-2026-53666 affects React Router, a router for React, in versions 6.4.0 through 7.17.0. Under specific conditions in Framework Mode and Data Mode with manual SSR/hydration, an attacker could trigger unexpected client-side constructor execution and outbound network requests by overwriting certain aspects of errors caught by the SSR process. This issue is fixed in version 7.18.0 and does not impact applications using Declarative Mode. The vulnerability allows attacker-supplied input to potentially overwrite error aspects caught by the SSR process, triggering unexpected constructor execution and outbound network requests. Organizations should assess and update to version 7.18.0 to mitigate potential risks. It is recommended to review application-layer code for potential vulnerabilities and implement compensating controls.

Vendor
remix-run
Product
react-router
CVSS
MEDIUM 6.1
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-27
Original CVE updated
2026-08-03
Advisory published
2026-07-27
Advisory updated
2026-08-03

Who should care

Developers and administrators of applications using React Router in Framework Mode and Data Mode with manual SSR/hydration, particularly those in versions 6.4.0 through 7.17.0, should be aware of this vulnerability and take steps to mitigate potential risks.

Technical summary

CVE-2026-53666 affects React Router versions 6.4.0 through 7.17.0 in Framework Mode and Data Mode with manual SSR/hydration. An attacker could, under specific conditions, trigger unexpected client-side constructor execution and outbound network requests by overwriting certain aspects of errors caught by the SSR process. This issue is fixed in version 7.18.0 and does not impact applications using Declarative Mode.

Defensive priority

Organizations using React Router versions 6.4.0 through 7.17.0, particularly those in Framework Mode and Data Mode with manual SSR/hydration, should assess and update to version 7.18.0 to mitigate potential client-side constructor execution and outbound network request risks.

Recommended defensive actions

  • Inventory and assess React Router usage, focusing on versions 6.4.0 through 7.17.0 in Framework Mode and Data Mode with manual SSR/hydration.
  • Update vulnerable React Router instances to version 7.18.0 or later.
  • Review application-layer code for potential vulnerabilities allowing attacker-supplied input to overwrite error aspects in SSR/hydration processes.
  • Implement compensating controls, such as monitoring for unexpected network requests triggered by client-side constructor execution.
  • Verify and document the effectiveness of applied mitigations and updates.

Evidence notes

The CVE details indicate that React Router versions 6.4.0 through 7.17.0 are vulnerable under specific conditions in Framework Mode and Data Mode with manual SSR/hydration. The issue allows attacker-supplied input to potentially overwrite error aspects caught by the SSR process, triggering unexpected constructor execution and outbound network requests. This does not affect applications using Declarative Mode.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-53666 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-53666

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-53666 NVD vulnerability detail

    Publisher, destination, and source semantics verified

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

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.