CVE-2021-43812 is a medium-severity (CVSS 6.1) Open Redirect vulnerability in @auth0/nextjs-auth0. A fix is available for @auth0/nextjs-auth0 — see the affected versions and patch details below.
Open redirect in @auth0/nextjs-auth0
EPSS Exploitation Probability
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.
How urgent is this, really
CVE-2021-43812 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@auth0/nextjs-auth0npmDescription
Overview
Versions <=1.6.1 do not filter out certain returnTo parameter values from the login url, which expose the application to an open redirect vulnerability.
Am I affected?
You are affected by this vulnerability if you are using @auth0/nextjs-auth0 version <=1.6.1.
How to fix that?
Upgrade to version >=1.6.2
Will this update impact my users?
The fix provided in the patch will not affect your users.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @auth0/nextjs-auth0 | all versions | 1.6.2npm install @auth0/nextjs-auth0@1.6.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @auth0/nextjs-auth0, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @auth0/nextjs-auth0 to 1.6.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43812 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-43812 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-43812. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-43812 in your dependencies?
O3 Security finds CVE-2021-43812 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.