How severe is GHSA-f46r-rw29-r322?

GHSA-f46r-rw29-r322 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-f46r-rw29-r322?

GHSA-f46r-rw29-r322 affects the following packages: react-router (npm). Ecosystems affected: npm.

How do I fix GHSA-f46r-rw29-r322?

Update react-router to 7.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f46r-rw29-r322 is resolved across your whole dependency graph.

How do I detect GHSA-f46r-rw29-r322 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for react-router. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-f46r-rw29-r322 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-f46r-rw29-r322?

O3 pinpoints whether GHSA-f46r-rw29-r322 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-f46r-rw29-r322 actively exploited in the wild?

No public exploit code has been indexed for GHSA-f46r-rw29-r322 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-f46r-rw29-r322?

GHSA-f46r-rw29-r322 has an EPSS (Exploit Prediction Scoring System) score of 22.0%, placing it in the 97th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

What type of vulnerability is GHSA-f46r-rw29-r322?

GHSA-f46r-rw29-r322 is classified as CWE-755 (CWE-755). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-f46r-rw29-r322 published, and has it been updated?

GHSA-f46r-rw29-r322 was published on April 24, 2025 and was last updated on April 25, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

GHSA-f46r-rw29-r322

HIGH

React Router allows a DoS via cache poisoning by forcing SPA mode

Also known asCVE-2025-43864

Published

Apr 24, 2025

Updated

Apr 25, 2025

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

22.0%probability of exploitation in next 30 days

Moderate Risk97th percentile+21.62%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

📦react-router

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.

Description

Summary

After some research, it turns out that it is possible to force an application to switch to SPA mode by adding a header to the request. If the application uses SSR and is forced to switch to SPA, this causes an error that completely corrupts the page. If a cache system is in place, this allows the response containing the error to be cached, resulting in a cache poisoning that strongly impacts the availability of the application.

Details

The vulnerable header is X-React-Router-SPA-Mode; adding it to a request sent to a page/endpoint using a loader throws an error. Here is the vulnerable code :

To use the header, React-router must be used in Framework mode, and for the attack to be possible the target page must use a loader.

Steps to reproduce

Versions used for our PoC:

"@react-router/node": "^7.5.0",
"@react-router/serve": "^7.5.0",
"react": "^19.0.0"
"react-dom": "^19.0.0"
"react-router": "^7.5.0"

Install React-Router with its default configuration in Framework mode (https://reactrouter.com/start/framework/installation)
Add a simple page using a loader (example: routes/ssr)

Send a request to the endpoint using the loader (/ssr in our case) adding the following header:

X-React-Router-SPA-Mode: yes

Notice the difference between a request with and without the header;

Normal request Capture d’écran 2025-04-07 à 08 36 27

With the header Capture d’écran 2025-04-07 à 08 37 01

Impact

If a system cache is in place, it is possible to poison the response by completely altering its content (by an error message), strongly impacting its availability, making the latter impractical via a cache-poisoning attack.

Credits

Rachid Allam (zhero;)
Yasser Allam (inzo_)

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`react-router`	≥ 7.2.0&&< 7.5.2	7.5.2

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for react-router. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update react-router to 7.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f46r-rw29-r322 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-f46r-rw29-r322 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-f46r-rw29-r322. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## Summary After some research, it turns out that it is possible to force an application to switch to SPA mode by adding a header to the request. If the application uses SSR and is forced to switch to SPA, this causes an error that completely corrupts the page. If a cache system is in place, this allows the response containing the error to be cached, resulting in a cache poisoning that strongly impacts the availability of the application. ## Details The vulnerable header is `X-React-Router-SPA-Mode`; adding it to a request sent to a page/endpoint using a loader throws an error. Here is [the v

O3 Security · Impact-Aware SCA

Is GHSA-f46r-rw29-r322 in your dependencies?

O3 detects GHSA-f46r-rw29-r322 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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