# CVE-2021-43812: Open redirect in nextjs-auth0

> An open redirect vulnerability in the Auth0 Next.js SDK allows attackers to redirect users to malicious sites via the returnTo parameter.

- **Severity:** Medium 6.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 16 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-2mqv-4j3r-vjvp

## What is CVE-2021-43812?

CVE-2021-43812 is a medium-severity vulnerability in nextjs-auth0, published on 16 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The Auth0 Next.js SDK is a library for implementing user authentication in Next.js applications. Versions before 1.6.2 do not filter out certain returnTo parameter values from the login url, which expose the application to an open redirect vulnerability. Users are advised to upgrade as soon as possible. There are no known workarounds for this issue.

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

## Which versions are affected by CVE-2021-43812?

2 open source packages ship an affected version, including @auth0/nextjs-auth0. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@auth0/nextjs-auth0` | npm | All versions | 1.6.2 |
| `@auth0/nextjs-auth0` | npm | All versions | 1.6.2 |

Products: Auth0 Nextjs-Auth0.

## How do I fix CVE-2021-43812?

Upgrade @auth0/nextjs-auth0 to 1.6.2 or later.

## Is CVE-2021-43812 being exploited?

There is no known exploitation of CVE-2021-43812 in the wild and no public exploit code.

## Other vulnerabilities in nextjs-auth0

- [CVE-2021-32702](https://insights.sbomify.com/CVE-2021-32702/): Reflected XSS from the callback handler's error query parameter (high 8.0)
- [CVE-2025-67716](https://insights.sbomify.com/CVE-2025-67716/): Auth0 Next.js SDK has Improper Validation of Query Parameters (medium 5.7)
- [CVE-2026-40155](https://insights.sbomify.com/CVE-2026-40155/): Auth0 Next.js SDK has Improper Proxy Cache Lookup (medium 5.4)
- [CVE-2025-67490](https://insights.sbomify.com/CVE-2025-67490/): Auth0 Next.js SDK has Improper Request Caching Lookup (medium 5.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43812 and fix it if it is affected.

What it is: CVE-2021-43812 is a medium-severity vulnerability in nextjs-auth0, published on 16 Dec 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-43812 in the wild and no public exploit code.

Affected packages and fixed versions:
- @auth0/nextjs-auth0 (npm): affected all versions; fixed in 1.6.2
- @auth0/nextjs-auth0 (npm): affected all versions; fixed in 1.6.2

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-2021-43812/ (Markdown: https://insights.sbomify.com/CVE-2021-43812/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43812
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43812
- OSV: https://osv.dev/vulnerability/CVE-2021-43812

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43812/
Summaries are generated and may contain mistakes; the official description above is the record.