CVE-2026-53666

MEDIUMPre-NVD 6.16.1—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4% (34th percentile of EPSS-scored CVEs). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
6.1EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0.4%CVSS: 6.1Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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.

CVSS v3
6.1
EG Score
6.1MEDIUMmedium confidence
EG Risk
28
EG Risk 28/100CISA SSVC

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity61% × 45%
Exploitation0% × 40%
Automatability0% × 15%
CISA SSVC: Track at every mission impact level.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.4%
EPSS %ILE
34th
KEV
Not listed

CISA SSVCTrack at every mission impact level.

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

July 23, 2026

Last Modified

August 3, 2026

Advisory Details (5)

Auto-updated Jul 27, 2026
Patch available. Sources: github, github_pr, github_commit, github_release.
github_release Patch Available

v7.18.0

Patch available: remix-run/react-router [email protected]

https://github.com/remix-run/react-router/releases/tag/[email protected]
generic

react-router/CHANGELOG.md at main · remix-run/react-router · GitHub

https://github.com/remix-run/react-router/blob/main/CHANGELOG.md#v7180
github_commit Patch Available

commit 9d22943fd46c (remix-run/react-router)

Patch available: remix-run/react-router [email protected] (contains commit 9d22943fd46c)

https://github.com/remix-run/react-router/commit/9d22943fd46c8ae4b08236425fa3549e10e9ad1a
github_pr Patch Available

Use turbo stream for framework hydration errors

Patch available: remix-run/react-router [email protected] (PR #15175 merged 2026-06-11)

https://github.com/remix-run/react-router/pull/15175
githubMentions a patch (unverified)

Arbitrary client-side constructor injection via React Router SSR Hydration · Advisory · remix-run/react-router · GitHub

https://github.com/remix-run/react-router/security/advisories/GHSA-337j-9hxr-rhxg

Vendor Advisories for CVE-2026-53666(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFix by version rangeDependents
react-router—
  • 6.4.0 up to 7.18.0: fixed in 7.18.0
—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 37× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 115 total refreshes for this CVE.

  1. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:12 UTCEPSS rescore
  3. 2026-10-07 23:48 UTCEPSS rescore
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  1. 2026-09-18 03:44 UTCEG score recompute
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  27. 2026-08-30 19:17 UTCEPSS rescore
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  43. 2026-08-20 22:55 UTCEPSS rescore
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  75. 2026-08-03 14:13 UTCEG score recompute

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Frequently asked(5)

What is CVE-2026-53666?
CVE-2026-53666 is a medium vulnerability published on July 23, 2026. 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…
When was CVE-2026-53666 disclosed?
CVE-2026-53666 was first published on July 23, 2026, with the most recent update on August 3, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-53666 actively exploited?
CVE-2026-53666 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.4% probability of exploitation in the next 30 days (34th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-53666?
CVE-2026-53666 has a CVSS base score of 6.1 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-53666?
A fix for CVE-2026-53666 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-53666 are linked in the Vendor Advisories panel on this page.

Dependency Blast Radius

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