CVE-2025-43864Public exploitNetwork attack vector

Denial of service via trusted SPA header

Published Apr 25, 2025 · Updated Apr 25, 2025

Denial of service in React Router 7.2.0 through 7.5.1 allows remote attackers to corrupt cached SSR responses via a request header. The server runtime trusts the X-React-Router-SPA-Mode build-time header at runtime, switches an SSR request to SPA mode, and throws on loader-backed routes. Exploitation requires Framework Mode, SSR, a loader-backed route, and a cache that stores the resulting error response, which can leave the affected page persistently unusable.

CVSS severity7.5
High
EPSS probability20.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in React Router 7.2.0 through 7.5.1 allows remote attackers to corrupt cached SSR responses via a request header. The server runtime trusts the X-React-Router-SPA-Mode build-time header at runtime, switches an SSR request to SPA mode, and throws on loader-backed routes. Exploitation requires Framework Mode, SSR, a loader-backed route, and a cache that stores the resulting error response, which can leave the affected page persistently unusable.

The record

CVE
CVE-2025-43864
Published
Apr 25, 2025
Updated
Apr 25, 2025
Vendor
Shopify
Product
React Router
Classifications
CWE-755, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 25, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 25, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 7.2.0, < 7.5.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Shopify · React Routerversion=>= 7.2.0, < 7.5.2

Published CVSS scores

7.5GitHub CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-755Improper Handling of Exceptional Conditions
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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