How severe is CVE-2026-42342?

CVE-2026-42342 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2026-42342 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42342?

CVE-2026-42342 primarily affects Shopify React-router. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-42342?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-42342 have an EU (EUVD) identifier?

Yes. CVE-2026-42342 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-34000.

When was CVE-2026-42342 published?

CVE-2026-42342 was published on 2026-06-02 and last updated on 2026-06-17.

CVE-2026-42342

CVE-2026-42342 is a high-severity vulnerability in Shopify React-router with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-400.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (22nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-34000
Weakness: CWE-400
Affected product: Shopify React-router
Published: 2026-06-02
Last modified: 2026-06-17

Description

React Router is a router for React. In versions 7.0.0 through 7.14.x of react-router and versions 2.10.0 through 2.17.4 of @remix-run/server-runtime, certain crafted requests can consume disproportionate server resources via unbounded path expansion in the __manifest endpoint, resulting in response time degradation and/or service unavailability for end users. This affects React Router Framework Mode applications as well as Remix applications. This does not impact applications using Declarative Mode (`<BrowserRouter>`) or Data Mode (`createBrowserRouter/<RouterProvider>`). This is patched in react-router version 7.15.0 and @remix-run/server-runtime version 2.17.5.

Frequently asked questions

What is CVE-2026-42342?: React Router is a router for React. In versions 7.0.0 through 7.14.x of react-router and versions 2.10.0 through 2.17.4 of @remix-run/server-runtime, certain crafted requests can consume disproportionate server resources via unbounded path expansion in the __manifest endpoint, resulting in response time degradation and/or service unavailability for end users. This affects React Router Framework Mode applications as well as Remix applications. This does not impact applications using Declarative Mode (`<BrowserRouter>`) or Data Mode (`createBrowserRouter/<RouterProvider>`). This is patched in react-router version 7.15.0 and @remix-run/server-runtime version 2.17.5.
How severe is CVE-2026-42342?: CVE-2026-42342 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-42342 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (22nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42342?: CVE-2026-42342 primarily affects Shopify React-router. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-42342?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-42342 have an EU (EUVD) identifier?: Yes. CVE-2026-42342 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-34000.
When was CVE-2026-42342 published?: CVE-2026-42342 was published on 2026-06-02 and last updated on 2026-06-17.

References

https://github.com/remix-run/react-router/security/advisories/GHSA-8x6r-g9mw-2r78

Affected products (2)

cpe:2.3:a:shopify:react-router:*:*:*:*:*:node.js:*:*
cpe:2.3:a:shopify:remix-run\/server-runtime:*:*:*:*:*:node.js:*:*

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