# CVE-2026-40181: React Router's same-origin redirect with path starting // causes open redirect via protocol-relative URL reinterpretation

> Attackers can exploit protocol-relative URL handling in React Router to redirect users to external domains, bypassing same-origin restrictions.

- **Severity:** Medium 6.6 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Jun 2026
- **Updated:** 4 Aug 2026
- **Also known as:** CLSA-2026-1788255151, CLSA-2026-1789597929, CLSA-2026-1792253404, CLSA-2026-1792419117, CLSA-2026-1792419192, CLSA-2026-1792419271, CLSA-2026-1792419627, CLSA-2026-1792421945, CLSA-2026-1792424734, CLSA-2026-1792425409, CLSA-2026-1792428111, CLSA-2026-1792430034, CLSA-2026-1793292226, GHSA-2j2x-hqr9-3h42, MINI-frfh-fpw5-6fcc, MINI-pm52-5crc-m84q, MINI-r8pr-4g64-xqjx, ROOT-APP-NPM-CVE-2026-40181

## What is CVE-2026-40181?

CVE-2026-40181 is a medium-severity vulnerability in @remix-run/router, published on 2 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

React Router is a router for React. In versions 7.0.0 through 7.14.0 and 6.7.0 through 6.30.3, certain URLs passed to the redirect function can trigger an open redirect to an external domain due to path values starting with // being reinterpreted as protocol-relative URLs. The level of impact depends on the validation done by the application prior to returning the redirect. This does not impact applications using Declarative Mode (<BrowserRouter>). This is patched in versions 7.14.1 and 6.30.4.

Weakness: CWE-601 (URL Redirection to Untrusted Site)

## Which versions are affected by CVE-2026-40181?

6 open source packages ship an affected version, including @remix-run/router and react-router. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@remix-run/router` | npm | From 1.3.0 | 1.23.3 |
| `@remix-run/router` | npm | From 1.3.0 | 1.23.3 |
| `react-router` | npm | From 6.7.0 | 6.30.4 |
| `react-router` | npm | From 6.7.0 | 6.30.4 |
| `react-router` | npm | From 7.0.0 | 7.14.1 |
| `react-router` | npm | From 7.0.0 | 7.14.1 |

Products: Shopify React-Router.

## How do I fix CVE-2026-40181?

Upgrade @remix-run/router to 1.23.3 or later.

## Is CVE-2026-40181 being exploited?

There is no known exploitation of CVE-2026-40181 in the wild and no public exploit code.

## Other vulnerabilities in @remix-run/router

- [CVE-2026-55685](https://insights.sbomify.com/CVE-2026-55685/): React Router: Unauthenticated Denial of Service via Inefficient Route Matching (high 8.7)
- [CVE-2026-21884](https://insights.sbomify.com/CVE-2026-21884/): React Router SSR XSS in ScrollRestoration (high 8.2)
- [CVE-2026-42211](https://insights.sbomify.com/CVE-2026-42211/): React Router's vendored turbo-stream v2 allows arbitrary constructor invocation via TYPE_ERROR deserialization leading to Unauth RCE (high 8.1)
- [CVE-2026-33245](https://insights.sbomify.com/CVE-2026-33245/): React Router vulnerable to XSS in unstable RSC redirect handling via javascript: redirect targets (high 8.0)
- [CVE-2026-22029](https://insights.sbomify.com/CVE-2026-22029/): React Router vulnerable to XSS via Open Redirects (high 8.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40181 and fix it if it is affected.

What it is: CVE-2026-40181 is a medium-severity vulnerability in @remix-run/router, published on 2 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-40181 in the wild and no public exploit code.

Affected packages and fixed versions:
- @remix-run/router (npm): affected from 1.3.0; fixed in 1.23.3
- @remix-run/router (npm): affected from 1.3.0; fixed in 1.23.3
- react-router (npm): affected from 6.7.0; fixed in 6.30.4
- react-router (npm): affected from 6.7.0; fixed in 6.30.4
- react-router (npm): affected from 7.0.0; fixed in 7.14.1
- react-router (npm): affected from 7.0.0; fixed in 7.14.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40181/ (Markdown: https://insights.sbomify.com/CVE-2026-40181/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40181
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40181
- OSV: https://osv.dev/vulnerability/CVE-2026-40181

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40181/
Summaries are generated and may contain mistakes; the official description above is the record.