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React Router vulnerable to Denial of Service via reflected user input in single-fetch

High severity GitHub Reviewed Published Jun 2, 2026 in remix-run/react-router

Package

npm react-router (npm)

Affected versions

>= 7.0.0, < 7.14.0

Patched versions

7.14.0
npm turbo-stream (npm)
< 3.0.0
3.0.0

Description

A DoS vulnerability exists in the React Router v7 Framework Mode, as well as Remix v2.9.0+ with Single Fetch enabled. In some scenarios the underlying serialization algorithm can become a bottleneck when encoding specific types of data into server responses. Please upgrade to React Router v7.14.0 or later.

Note

This does not impact your React Router application if you are using Declarative Mode (<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>).

References

@brophdawg11 brophdawg11 published to remix-run/react-router Jun 2, 2026
Published by the National Vulnerability Database Jun 2, 2026
Published to the GitHub Advisory Database Jun 4, 2026
Reviewed Jun 4, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(18th percentile)

Weaknesses

Allocation of Resources Without Limits or Throttling

The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. Learn more on MITRE.

CVE ID

CVE-2026-34077

GHSA ID

GHSA-rxv8-25v2-qmq8

Source code

Credits

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